Semiconductor device including SGT

ABSTRACT

A surround gate MOS transistor (SGT) includes a silicon pillar and tungsten silicide or cobalt silicide wiring alloy layers constituted by first alloy regions connected to the entire peripheries of impurity regions serving as sources or drains in lower portions of the silicon pillar. The first alloy regions are formed in a self-aligned manner with the impurity regions in a tubular shape, and contain the same impurity atoms as the impurity regions. A second alloy region is partly connected to the peripheries of the first alloy regions and contains the same impurity atoms as the impurity regions.

RELATED APPLICATIONS

This application is a divisional patent application of U.S. application Ser. No. 15/917,168, filed Mar. 9, 2018, which is a continuation-in-part application of PCT/JP2015/085469, filed Dec. 18, 2015, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a semiconductor device including a surrounding gate MOS transistor (SGT) and a method for producing the semiconductor device.

2. Description of the Related Art

In recent years, semiconductor devices including SGTs have been required to have higher density and higher performance.

In planar MOS transistors, the channel of a P- or N-channel MOS transistor is formed in a horizontal direction along the surface of a semiconductor substrate between the source and the drain. In contrast, the channel of an SGT is formed in a direction vertical to the surface of a semiconductor substrate (e.g., refer to Japanese Unexamined Patent Application Publication No. 2-188966 and Hiroshi Takato, Kazumasa Sunouchi, Naoko Okabe, Akihiro Nitayama, Katsuhiko Hieda, Fumio Horiguchi, and Fujio Masuoka: IEEE Transaction on Electron Devices, Vol. 38, No. 3, pp. 573-578 (1991)).

FIG. 12 schematically illustrates a structure of an N-channel SGT. N⁺ regions 116 a and 116 b are formed in a lower portion and an upper portion of a P-type or i-type (intrinsic) Si pillar 115 (hereafter a silicon semiconductor pillar is referred to as a “Si pillar”). When one of the N⁺ regions 116 a and 116 b functions as a source, the other functions as a drain. A portion of the Si pillar 115 between the source and drain N⁺ regions 116 a and 116 b is a channel region 117. A gate insulating layer 118 is formed so as to surround the channel region 117, and a gate conductor layer 119 is formed so as to surround the gate insulating layer 118. In an SGT, the source and drain N⁺ regions 116 a and 116 b, the channel region 117, the gate insulating layer 118, and the gate conductor layer 119 are formed in a single Si pillar 115. Therefore, the area of the surface of the SGT appears to be equal to the area of one source or drain N⁺ region of a planar MOS transistor. Thus, circuit chips including SGTs can achieve further chip-size reduction compared with circuit chips including planar MOS transistors.

FIG. 13 is a sectional view of a CMOS inverter circuit including SGTs (e.g., refer to FIG. 38(b) in U.S. Patent Application Publication No. 2010/0264484).

In this CMOS inverter circuit, an i layer 121 (the “i layer” refers to an intrinsic Si layer) is formed on an insulating layer substrate 120, and a Si pillar SP1 for a P-channel SGT and a Si pillar SP2 for an N-channel SGT are formed on the i layer 121.

A drain P⁺ region 122 of the P-channel SGT is formed in the same layer as the i layer 121 so as to surround a lower portion of the Si pillar SP1 in plan view. A drain N⁺ region 123 of the N-channel SGT is formed in the same layer as the i layer 121 so as to surround a lower portion of the Si pillar SP2 in plan view.

A source P⁺ region 124 of the P-channel SGT is formed in a top portion of the Si pillar SP1, and a source N⁺ region 125 of the N-channel SGT is formed in a top portion of the Si pillar SP2.

Gate insulating layers 126 a and 126 b are formed on upper surfaces of the P⁺ region 122 and N⁺ region 123 so as to extend along and surround the Si pillars SP1 and SP2. A gate conductor layer 127 a of the P-channel SGT and a gate conductor layer 127 b of the N-channel SGT are formed so as to surround the gate insulating layers 126 a and 126 b.

Sidewall nitride films 128 a and 128 b serving as insulating layers are formed so as to surround the gate conductor layers 127 a and 127 b. Similarly, sidewall nitride films 128 c and 128 d serving as insulating layers are formed so as to surround a P⁺ region and an N⁺ region in top portions of the Si pillars SP1 and SP2.

The drain P⁺ region 122 of the P-channel SGT and the drain N⁺ region 123 of the N-channel SGT are connected to each other through a silicide layer 129 b. A silicide layer 129 a is formed on the source P⁺ region 124 of the P-channel SGT, and a silicide layer 129 c is formed on the source N⁺ region 125 of the N-channel SGT. Furthermore, silicide layers 129 d and 129 e are formed in top portions of the gate conductor layers 127 a and 127 b.

An i layer 130 a of the Si pillar SP1 that lies between the P⁺ regions 122 and 124 functions as a channel of the P-channel SGT. An i layer 130 b of the Si pillar SP2 that lies between the N⁺ regions 123 and 125 functions as a channel of the N-channel SGT.

A SiO₂ layer 131 is formed so as to cover the insulating layer substrate 120, the i layer 121, and the Si pillars SP1 and SP2. Furthermore, contact holes 132 a, 132 b, and 132 c are formed so as to extend through the SiO₂ layer 131. The contact hole 132 a is formed on the Si pillar SP1, the contact hole 132 c is formed on the Si pillar SP2, and the contact hole 132 b is formed on the drain P⁺ region 122 of the P-channel SGT and the N⁺ region 123 of the N-channel SGT.

A power supply wiring metal layer Vd formed on the SiO₂ layer 131 is connected to the source P⁺ region 124 of the P-channel SGT and the silicide layer 129 a through the contact hole 132 a. An output wiring metal layer Vo formed on the SiO₂ layer 131 is connected to the drain P⁺ region 122 of the P-channel SGT, the drain N⁺ region 123 of the N-channel SGT, and the silicide layer 129 b through the contact hole 132 b. A ground wiring metal layer Vs formed on the SiO₂ layer 131 is connected to the source N⁺ region 125 of the N-channel SGT and the silicide layer 129 c through the contact hole 132 c.

The gate conductor layer 127 a of the P-channel SGT and the gate conductor layer 127 b of the N-channel SGT are connected to an input wiring metal layer (not illustrated) while being connected to each other.

In this CMOS inverter circuit, the P-channel SGT and the N-channel SGT are formed in the Si pillars SP1 and SP2. Therefore, the circuit area is reduced when vertically viewed in plan. As a result, a further reduction in the size of the circuit is achieved compared with CMOS inverter circuits including known planar MOS transistors.

The CMOS inverter circuit including SGTs illustrated in FIG. 13 has also been required to have higher density and higher performance. However, the following problems arise when the density and performance of this circuit are further improved.

1. In the mask design for the Si pillars SP1 and SP2 and the i layer 121, margins need to be left in terms of shape and positional relationship to accurately form the Si pillars SP1 and SP2 on the i layer 121 with certainty. This inhibits the increase in the density of the circuit.

2. The resistances between the end of the silicide layer 129 b and the P⁺ region 122 directly below the Si pillar SP1 and between the end of the silicide layer 129 b and the N⁺ region 123 directly below the Si pillar SP2 decrease the driving current and the driving speed.

3. A thin gate insulating layer 126 a lies between the gate conductor layer 127 a and the P⁺ region 122. Therefore, a large coupling capacitance is present between the gate conductor layer 127 a and the P⁺ region 122. Similarly, a thin gate insulating layer 126 b lies between the gate conductor layer 127 b and the N⁺ region 123. Therefore, a large coupling capacitance is present between the gate conductor layer 127 b and the N⁺ region 123. Such large coupling capacitances inhibit the increase in the speed.

4. Thin sidewall nitride films 128 a and 128 b lie between the contact hole 132 b and the gate conductor layers 127 a and 127 b. Therefore, large coupling capacitances are present between the gate conductor layers 127 a and 127 b and the output wiring metal layer Vo. Such large coupling capacitances inhibit the increase in the speed. If the coupling capacitance is decreased by increasing the thicknesses of the sidewall nitride films 128 a and 128 b, the circuit area increases.

Accordingly, the density and performance of the circuit need to be improved by addressing the above problems.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a semiconductor device including an SGT for improving the density and performance of a circuit and a method for producing the semiconductor device.

A semiconductor device including an SGT according to a first aspect of the present invention includes a first semiconductor pillar that stands on a substrate in a direction vertical to a plane of the substrate; a first gate insulating layer that surrounds the first semiconductor pillar; a first gate conductor layer that surrounds the first gate insulating layer; a first impurity region that is positioned below the gate conductor layer in the vertical direction and is connected to a portion inside the first semiconductor pillar or to a side surface of the first semiconductor pillar; a first conductive layer that surrounds an entire periphery of the first impurity region in plan view; a second conductive layer that is partly connected to a periphery of the first conductive layer in plan view and extends in a direction horizontal to the plane of the substrate; a third conductive layer that surrounds an entire periphery of the first gate conductor layer in plan view; and a fourth conductive layer that is partly connected to a periphery of the third conductive layer in plan view, extends in a direction horizontal to the plane of the substrate, and partly overlaps the second conductive layer or does not overlap the second conductive layer in plan view, wherein at least one of the first conductive layer and the third conductive layer has an equal width in plan view.

In the semiconductor device, a center line of the fourth conductive layer that extends in a belt-like shape with an equal width from a portion in contact with the third conductive layer in plan view preferably extends in an extension direction of the fourth conductive layer so as not to pass through a center point of the first semiconductor pillar.

In the semiconductor device, the first conductive layer, the second conductive layer, and the first impurity region preferably contain the same donor or acceptor impurity atom.

In the semiconductor device, the first conductive layer and the first impurity region are preferably connected to each other in a self-aligned manner.

In the semiconductor device, the first gate conductor layer and the third conductive layer are preferably connected to each other in a self-aligned manner.

The semiconductor device preferably further includes a fifth conductive layer that is in contact with an inner side surface of the first conductive layer, is positioned between the first conductive layer and the first impurity region, and contains the same metal atom and donor or acceptor impurity atom as the first conductive layer.

The semiconductor device preferably includes a second semiconductor pillar that vertically stands so as to be adjacent to the first semiconductor pillar; a second gate insulating layer that surrounds the second semiconductor pillar; a second gate conductor layer that surrounds the second gate insulating layer; a second impurity region that is positioned below the second gate conductor layer in the vertical direction and is connected to a portion inside the second semiconductor pillar or to a side surface of the second semiconductor pillar; a sixth conductive layer that surrounds the second impurity region in plan view; and a seventh conductive layer that surrounds the second gate conductor layer in plan view. Preferably, at least one of the sixth conductive layer and the seventh conductive layer has an equal width, the second conductive layer is partly in contact with the sixth conductive layer, and the fourth conductive layer is partly in contact with the seventh conductive layer.

The semiconductor device preferably includes an eighth conductive layer that partly surrounds a periphery of the first conductive layer with an equal width in plan view; a ninth conductive layer that partly surrounds a periphery of the sixth conductive layer with an equal width in plan view; and a tenth conductive layer that lies between the first semiconductor pillar and the second semiconductor pillar in plan view so as to be in contact with the first conductive layer, the sixth conductive layer, the eighth conductive layer, and the ninth conductive layer.

The semiconductor device preferably includes an eleventh conductive layer that partly surrounds a periphery of the third conductive layer with an equal width in plan view; a twelfth conductive layer that partly surrounds a periphery of the seventh conductive layer with an equal width in plan view; and a thirteenth conductive layer that lies between the first semiconductor pillar and the second semiconductor pillar in plan view so as to be in contact with the third conductive layer, the seventh conductive layer, the eleventh conductive layer, and the twelfth conductive layer.

The semiconductor device preferably includes the first impurity region that surrounds a side surface of the first semiconductor pillar with an equal width in plan view; and the first conductive layer that surrounds the first impurity region with an equal width in plan view.

In the semiconductor device, at least one of the first conductive layer and the third conductive layer is preferably constituted by a plurality of material layers having an equal width in plan view.

In the semiconductor device, the first conductive layer and the second conductive layer are preferably formed of the same material and/or the third conductive layer and the fourth conductive layer are preferably formed of the same material.

A method for producing a semiconductor device including an SGT according to a second aspect of the present invention includes a step of forming a first semiconductor pillar that stands on a substrate in a vertical direction; a step of forming a first gate insulating layer that surrounds the first semiconductor pillar; a step of forming a first gate conductor layer that surrounds the first gate insulating layer; a step of forming a first impurity region that is positioned below the first gate conductor layer in the vertical direction, is connected to a portion inside the first semiconductor pillar or to a side surface of the first semiconductor pillar, and contains a donor or acceptor impurity; a step of forming a first conductive layer that surrounds a periphery of the first semiconductor pillar in plan view and is in contact with the first gate conductor layer or the first impurity region; a step of forming, on the first conductive layer, a first material layer that surrounds a side surface of a periphery of the first semiconductor pillar with an equal width in plan view; a step of forming, on the first conductive layer, a second material layer that is partly in contact with the first material layer in plan view; and a step of etching the first conductive layer using the first material layer and the second material layer as masks, wherein, as a result of the etching of the first conductive layer, a second conductive layer that is in contact with the first gate conductor layer or the first impurity region and surrounds a side surface of a periphery of the first gate conductor layer or the first impurity region with an equal width in plan view and a third conductive layer that is partly in contact with the second conductive layer are formed.

The method preferably includes a step of forming the first impurity region by introducing a donor or acceptor impurity atom into the first conductive layer or the second conductive layer and the third conductive layer and performing heat treatment to force the donor or acceptor impurity atom toward an inside of the first semiconductor pillar from the first conductive layer or the second conductive layer and the third conductive layer.

The method preferably includes a step of forming the first impurity region by performing heat treatment after formation of the first conductive layer containing a donor or acceptor impurity atom or before or after formation of the second conductive layer and the third conductive layer, and forming a fourth conductive layer containing a metal atom and a donor or acceptor impurity atom between the second conductive layer and the first impurity region.

The method preferably includes a step of forming a third material layer that surrounds a side surface of the first semiconductor pillar and is formed of one or more layers after formation of the first material layer; and a step of forming the second conductive layer and the third conductive layer by etching the third material layer and the first conductive layer using the first material layer, the second material layer, and the top material layer as masks.

In the method, a fifth conductive layer that is the third conductive layer connected to the first impurity region and a sixth conductive layer that is the third conductive layer connected to the first gate conductor layer are preferably formed so as to be away from each other or partly overlap each other in plan view.

The method preferably includes a step of forming a second semiconductor pillar that is adjacent to the first semiconductor pillar; a step of forming a second gate insulating layer that surrounds the second semiconductor pillar and has the same height as the first gate insulating layer in the vertical direction; a step of forming a second gate conductor layer that surrounds the second gate insulating layer; a step of forming, around the second semiconductor pillar, a second impurity region that has the same height as the first impurity region in the vertical direction and contains a donor or acceptor impurity; a step of forming a seventh conductive layer that is in contact with the second impurity region in plan view; and a step of forming an eighth conductive layer that is in contact with the second gate conductor layer in plan view. At least one of the seventh conductive layer and the eighth conductive layer preferably has an equal width in plan view, the fifth conductive layer and the seventh conductive layer are preferably formed so as to be connected to each other on the same plane, and the sixth conductive layer and the eighth conductive layer are preferably formed so as to be connected to each other on the same plane.

The method preferably includes a step of forming fourth material layers that surround peripheries of the first semiconductor pillar and the second semiconductor pillar and are connected to each other in a portion between the first semiconductor pillar and the second semiconductor pillar; and a step of etching the first conductive layer using the fourth material layer as an etching mask to form a ninth conductive layer that surrounds an entire periphery of the first impurity region or the first gate conductor layer with an equal width in plan view, a tenth conductive layer that surrounds an entire periphery of the second impurity region or the second gate conductor layer with an equal width, an eleventh conductive layer that is partly connected to peripheries of the ninth conductive layer and the tenth conductive layer and extends in parallel with a surface of the substrate, and a twelfth conductive layer that is partly in contact with peripheries of the ninth conductive layer and the tenth conductive layer in plan view and has an equal width in plan view.

The method preferably includes a step of forming a fifth material layer that partly overlaps the fourth material layer in plan view after formation of the fourth material layer; and a step of etching the first impurity region or the first gate conductor layer using the fourth material layer and the fifth material layer as masks.

The method preferably includes a step of forming a sixth material layer on a periphery of the first semiconductor pillar after formation of the first material layer; a step of forming, on the sixth material layer, the second material layer that partly overlaps the first material layer in plan view; and a step of etching the sixth material layer and the first conductive layer using the first material layer and the second material layer as masks.

The method preferably includes a step of forming a seventh material layer that surrounds the first semiconductor pillar or the gate conductor layer, has an upper surface positioned lower than a top of the semiconductor pillar, and has a conductive or insulating property; a step of forming, on the seventh material layer, an eighth material layer that surrounds a top portion of the semiconductor pillar with an equal width; a step of forming a ninth material layer with an equal width in plan view by etching the seventh material layer using the eighth material layer as a mask; and a step of etching the first conductive layer using the eighth material layer and the ninth material layer as masks.

The method preferably includes a step of forming the first impurity region that surrounds a side surface of the first semiconductor pillar with an equal width in plan view; and a step of forming the first conductive layer that surrounds the first impurity region with an equal width in plan view.

In the method, the second conductive layer is preferably formed of a plurality of material layers having an equal width in plan view.

The method preferably includes a step of forming, on a top of the first semiconductor pillar, a top material layer to serve as an etching mask for the first conductive layer before the second material layer is formed.

The present invention can provide a semiconductor device including an SGT for improving the density and performance of a circuit and a method for producing the semiconductor device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1AA to 1AD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a first embodiment.

FIGS. 1BA to 1BD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a first embodiment.

FIGS. 1CA to 1CD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a first embodiment.

FIGS. 1DA to 1DD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a first embodiment.

FIGS. 1EA to 1ED are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a first embodiment.

FIGS. 1FA to 1FD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a first embodiment.

FIGS. 1GA to 1GD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a first embodiment.

FIGS. 1HA to 1HD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a first embodiment.

FIGS. 1IA to 1ID are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a first embodiment.

FIGS. 1JA to 1JE are plan views and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a first embodiment.

FIGS. 2AA to 2AD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a second embodiment.

FIGS. 2BA to 2BD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a second embodiment.

FIGS. 2CA to 2CE are plan views and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a second embodiment.

FIGS. 3AA to 3AD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a third embodiment.

FIGS. 3BA to 3BD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a third embodiment.

FIGS. 3CA to 3CD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a third embodiment.

FIGS. 3DA to 3DD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a third embodiment.

FIGS. 3EA to 3ED are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a third embodiment.

FIGS. 3FA to 3FD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a third embodiment.

FIGS. 4AA to 4AD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a fourth embodiment.

FIGS. 4BA to 4BD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a fourth embodiment.

FIGS. 4CA to 4CD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a fourth embodiment.

FIGS. 4DA to 4DD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a fourth embodiment.

FIGS. 5AA to 5AD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a fifth embodiment.

FIGS. 5BA to 5BD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a fifth embodiment.

FIGS. 5CA to 5CD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a fifth embodiment.

FIGS. 5DA to 5DD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a fifth embodiment.

FIGS. 6AA to 6AD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a sixth embodiment.

FIGS. 6BA to 6BE are plan views and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a sixth embodiment.

FIGS. 7AA to 7AD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a seventh embodiment.

FIGS. 7BA to 7BD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a seventh embodiment.

FIGS. 7CA to 7CD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a seventh embodiment.

FIGS. 8AA to 8AD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to an eighth embodiment.

FIGS. 8BA to 8BD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to an eighth embodiment.

FIGS. 8CA to 8CD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to an eighth embodiment.

FIGS. 8DA to 8DD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to an eighth embodiment.

FIGS. 9AA to 9AD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a ninth embodiment.

FIGS. 9BA to 9BD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a ninth embodiment.

FIGS. 10A to 10D are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to a tenth embodiment.

FIGS. 11AA to 11AD are a plan view and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to an eleventh embodiment.

FIGS. 11BA to 11BE are plan views and sectional views illustrating a CMOS inverter circuit for describing a method for producing a semiconductor device including an SGT according to an eleventh embodiment.

FIG. 12 schematically illustrates a structure of a known SGT.

FIG. 13 is a sectional view of a CMOS inverter circuit including a known SGT.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, a semiconductor device including an SGT and a method for producing the semiconductor device according to embodiments of the present invention will be described with reference to the attached drawings.

First Embodiment

FIG. 1AA to FIG. 1JE illustrate a method for producing a CMOS inverter circuit including an SGT according to a first embodiment of the present invention.

FIGS. 1AA to 1AD are a plan view and sectional views for describing the first production process of the CMOS inverter circuit including an SGT. FIG. 1AA is a plan view, FIG. 1AB is a sectional view taken along line X-X′ in FIG. 1AA, FIG. 1AC is a sectional view taken along line Y1-Y1′ in FIG. 1AA, and FIG. 1AD is a sectional view taken along line Y2-Y2′ in FIG. 1AA. In other figures referred to in the description below, the same applies to the relationship of views indicated by the suffixes A, B, C, and D.

As illustrated in FIGS. 1AA to 1AD, SiN layers 2 a and 2 b, SiO₂ layers 3 a and 3 b, and resist layers 5 a and 5 b are formed by depositing, from the bottom, a silicon nitride layer (SiN layer, not illustrated) and a SiO₂ layer (not illustrated) on an i layer substrate 1 and using a lithography technique such as reactive ion etching (RIE). The SiN layer 2 a, the SiO₂ layer 3 a, and the resist layer 5 a are stacked on the i layer substrate 1 in this order. The SiN layer 2 b, the SiO₂ layer 3 b, and the resist layer 5 b are stacked on the i layer substrate 1 in this order. A thin SiO₂ layer is desirably formed between the i layer substrate 1 and the SiN layer (not illustrated) to improve the processability of the SiN layer.

Next, as illustrated in FIGS. 1BA to 1BD, the i layer substrate 1 is etched by, for example, RIE using the SiN layers 2 a and 2 b, the SiO₂ layers 3 a and 3 b, and the resist layers 5 a and 5 b as etching masks. Thus, a lower portion of the i layer substrate 1 is left as an i layer substrate 1 a and Si pillars 4 a and 4 b are formed on the i layer substrate 1 a. Then, the resist layers 5 a and 5 b are removed. The Si pillar 4 a is located below the SiN layer 2 a and the SiO₂ layer 3 a and the Si pillar 4 b is located below the SiN layer 2 b and the SiO₂ layer 3 b.

Next, as illustrated in FIGS. 1CA to 1CD, for example, a bias sputtering process is carried out in the following manner: a substrate metal plate on which the i layer substrate 1 a is disposed and a facing metal plate located away from the substrate metal plate are provided; a direct-current voltage is applied to the substrate metal plate, and an RF voltage is applied across these two parallel metal plates, to thereby sputter the material atoms of the facing metal plate onto the i layer substrate 1 a. Thus, a SiO₂ layer 6, a WSi₂ layer 7, and a SiN layer 8 are formed. Subsequently, a lower SiO₂ layer (not illustrated), a WSi₂ layer (not illustrated), and an upper SiN layer (not illustrated) formed on the Si pillars 4 a and 4 b as a result of the bias sputtering process are removed. Since the Si pillars 4 a and 4 b are formed by RIE, the side surfaces of the Si pillars 4 a and 4 b are substantially vertical to the plane of the i layer substrate 1 a. Therefore, a SiO₂ film, a WSi₂ film, and a SiN film are not formed on the side surfaces of the Si pillars 4 a and 4 b (for the mechanism in which material atoms do not adhere to the side surfaces, refer to C. Y. Ting, V. J. Vivalda, and H. G. Schaefer: “Study of planarized sputter-deposited SiO₂” J. Vac. Sci. Technology, 15(3), May/June (1978)).

Next, as illustrated in FIGS. 1DA to 1DD, a resist layer 10 is formed so as to cover the Si pillar 4 b. Boron ions (B⁺) are implanted in a direction toward the upper surface of the i layer substrate 1 a using the resist layer 10 as a mask to form a WSi₂ layer 7 a containing B atoms on the periphery of the Si pillar 4 a. Then, the resist layer 10 is removed. Herein, a thin oxide film (not illustrated) serving as a protective film is desirably formed on the side surfaces of the Si pillars 4 a and 4 b by an oxidation process or an atomic layer deposition (ALD) process before the formation of the resist layer 10.

Subsequently, arsenic ions (Ask) are implanted using, as a mask, a resist layer (not illustrated) formed so as to cover the Si pillar 4 a. Thus, a WSi₂ layer 7 b containing As atoms is formed on the periphery of the Si pillar 4 b. Then, the resist layer is removed. A SiO₂ film (not illustrated) is entirely deposited by chemical vapor deposition (CVD). The SiO₂ film is etched by RIE so that a part of the SiO₂ film is left on the side surfaces of the Si pillars 4 a and 4 b. Thus, as illustrated in FIGS. 1EA to 1ED, SiO₂ layers 11 a and 11 b are formed on the side surfaces of the Si pillars 4 a and 4 b.

Next, as illustrated in FIGS. 1FA to 1FD, by performing heat treatment, the B atoms are forced toward the inside of the Si pillar 4 a from the WSi₂ layer 7 a to form a P⁺ region 12 a in the Si pillar 4 a, and the As atoms are forced toward the inside of the Si pillar 4 b from the WSi₂ layer 7 b to form an N⁺ region 12 b in the Si pillar 4 b (for the mechanism in which the P⁺ region 12 a and the N⁺ region 12 b are formed through the forcing phenomenon of impurity atoms, refer to V. Probst, H. Schaber, A. Mitwalsky, and H. Kabza: “WSi₂ and CoSi₂ as diffusion sources for shallow-junction formation in silicon”, J. Appl. Phys. Vol. 70(2), No. 15, pp. 708-719 (1991)).

Next, as illustrated in FIGS. 1GA to 1GD, a resist layer 13 that partly overlaps the Si pillars 4 a and 4 b in plan view is formed. The SiN layer 8 and the WSi₂ layers 7 a and 7 b are etched by RIE using the resist layer 13, the SiO₂ layers 11 a and 11 b, the SiO₂ layers 2 a and 2 b, and the SiN layers 3 a and 3 b as masks to form a SiN layer 8 a and WSi₂ layers 7 aa and 7 bb. In this case, the WSi₂ layers 7 aa and 7 bb lie below the SiO₂ layers 11 a and 11 b, and are constituted by first alloy regions that surround the entire peripheries of the Si pillars 4 a and 4 b in plan view and a second alloy region that is connected to the first alloy regions and lies below the resist layer 13. The first alloy regions of the WSi₂ layers 7 a and 7 b are self-aligned with the P⁺ region 12 a and the N⁺ region 12 b. That is, the first alloy regions of the WSi₂ layers 7 aa and 7 bb that lie below the SiO₂ layers 11 a and 11 b are formed in a tubular shape with an equal width so as to surround the entire peripheries of the P⁺ region 12 a and the N⁺ region 12 b regardless of the mask misalignment in lithography during formation of the resist layer 13.

Next, the resist layer 13 and the SiO₂ layers 11 a and 11 b are removed. Then, as illustrated in FIGS. 1HA to 1HD, a SiO₂ film (not illustrated) is entirely deposited by CVD and etched back to a position of an upper surface of the SiN layer 8 a to form a SiO₂ layer 14. Then, a HfO₂ layer 15 and a TiN layer 16 are entirely deposited by atomic layer deposition (ALD).

Next, as illustrated in FIGS. 1IA to 1ID, a SiO₂ film (not illustrated) is entirely deposited by CVD and etched back until the upper surface of the SiO₂ film is positioned lower than the tops of the Si pillars 4 a and 4 b to form a SiO₂ layer 18. Then, portions of the TiN layer 16, the HfO₂ layer 15, the SiO₂ layers 3 a and 3 b, and the SiN layers 2 a and 2 b positioned higher than the upper surface of the SiO₂ layer 18 are removed. The remaining portions of the TiN layer 16 and the HfO₂ layer 15 are referred to as a TiN layer 16 a and a HfO₂ layer 15 a. By performing lithography and ion implantation, a P⁺ region 19 a is formed in a top portion of the Si pillar 4 a and an N⁺ region 19 b is formed in a top portion of the Si pillar 4 b.

Next, as illustrated in FIGS. 1JA to 1JD, a SiO₂ layer 21 is formed on the SiO₂ layer 18 so as to cover the P⁺ region 19 a and the N⁺ region 19 b. Then, a contact hole 22 a is formed on the P⁺ region 19 a, a contact hole 22 b is formed on the N⁺ region 19 b, a contact hole 22 c is formed on the TiN layer 16 a, and a contact hole 22 d that is connected to the upper surfaces and side surfaces of the WSi₂ layers 7 aa and 7 bb is formed. The half-length of one side of the contact hole 22 d is desirably smaller than the thickness of the WSi₂ layers 7 aa and 7 bb in plan view. A power supply wiring metal layer Vdd connected to the P⁺ region 19 a through the contact hole 22 a is formed on the SiO₂ layer 21. A ground wiring metal layer Vss connected to the N⁺ region 19 b through the contact hole 22 b is formed on the SiO₂ layer 21. An input wiring metal layer Vin connected to the TiN layer 16 a through the contact hole 22 c is formed on the SiO₂ layer 21. An output wiring metal layer Vout connected to the WSi₂ layers 7 aa and 7 bb through the contact hole 22 d is formed on the SiO₂ layer 21.

Thus, a CMOS inverter circuit constituted by a P-channel SGT for load and an N-channel SGT for drive is formed. The P-channel SGT for load includes the P⁺ region 12 a as a source, the P⁺ region 19 a as a drain, the HfO₂ layer 15 a as a gate insulating layer, the TiN layer 16 a as a gate conductor layer, and a portion of the Si pillar 4 a between the P⁺ regions 12 a and 19 a as a channel. The N-channel SGT for drive includes the N⁺ region 12 b as a source, the N⁺ region 19 b as a drain, the HfO₂ layer 15 a as a gate insulating layer, the TiN layer 16 a as a gate conductor layer, and a portion of the Si pillar 4 b between the N⁺ regions 12 b and 19 b as a channel.

FIG. 1JE illustrates the relationship between the Si pillars 4 a and 4 b, the P⁺ region 12 a, the N⁺ region 12 b, and the WSi₂ layers 7 aa and 7 bb in plan view. The diagonally shaded area indicates the WSi₂ layers 7 aa and 7 bb. The WSi₂ layer 7 aa is constituted by a WSi₂ layer 7Aa serving as a first alloy region that surrounds the entire periphery of the Si pillar 4 a in a tubular shape with an equal width and is formed in a self-aligned manner with the P⁺ region 12 a and a WSi₂ layer 7Ab serving as a second alloy region that is partly in contact with the periphery of the WSi₂ layer 7Aa in a connected manner. Similarly, the WSi₂ layer 7 bb is constituted by a WSi₂ layer 7Ba serving as a first alloy region that surrounds the entire periphery of the Si pillar 4 b in a tubular shape with an equal width and is formed in a self-aligned manner with the N⁺ region 12 b and a WSi₂ layer 7Bb serving as a second alloy region that is partly in contact with the periphery of the WSi₂ layer 7Ba in a connected manner. The WSi₂ layers 7Ab and 7Bb are in contact with each other.

The first embodiment provides the following advantages.

1. In the related art, there has been a need to form the Si pillars SP1 and SP2 on the i layer 121 and introduce an impurity into the i layer 121 to form the P⁺ region 122 and the N⁺ region 123 as illustrated in FIG. 13. Therefore, in the mask design for the Si pillars SP1 and SP2 and the i layer 121, margins need to be left in terms of shape and positional relationship to accurately form the Si pillars SP1 and SP2 on the i layer 121 with certainty. This inhibits the increase in the density of the circuit. In contrast, in this embodiment, a marginal region for mask alignment that has been required is unnecessary. Furthermore, as illustrated in FIGS. 1GA to 1GD, the planar shape of the resist layer 13 in lithography, the resist layer 13 being formed for forming the WSi₂ layers 7 aa and 7 bb that surround the outer peripheries of the P⁺ region 12 a and the N⁺ region 12 b in a connected manner, may be a rectangle, which is the simplest shape. This can further increase the density of a circuit and can simplify the production process.

2. In this embodiment, as illustrated in FIG. 1JE, the WSi₂ layers 7Aa and 7Ba are formed as first alloy regions that are directly in contact with the side surfaces of the Si pillars 4 a and 4 b, that surround the entire peripheries of the Si pillars 4 a and 4 b in a tubular shape with an equal width in plan view, and that are in contact with the P⁺ region 12 a and the N⁺ region 12 b in a self-aligned manner. The presence of the WSi₂ layers 7Aa and 7Ba serving as low-resistance first alloy regions that surround the entire peripheries of the Si pillars 4 a and 4 b can generate a uniform electric field in the P⁺ region 12 a and the N⁺ region 12 b during circuit operation. This uniform electric field can be generated regardless of the planar shape of the WSi₂ layers 7Ab and 7Bb serving as second alloy regions. The WSi₂ layers 7Ab and 7Bb serving as second alloy regions may be connected to any parts of the WSi₂ layers 7Aa and 7Ba serving as first alloy regions. Thus, in terms of design, the WSi₂ layers 7Ab and 7Bb serving as second alloy regions may be formed without surrounding the Si pillars 4 a and 4 b. This can increase the density of a circuit and improve the performance of the circuit.

3. In this embodiment, the WSi₂ layers 7 a and 7 b containing acceptor and donor impurities, which will be changed into the WSi₂ layers 7 aa and 7 bb in a process performed later, are source layers for supplying acceptor and donor impurities used for forming the P⁺ regions 12 a and the N⁺ region 12 b in the Si pillars 4 a and 4 b. The WSi₂ layers 7 aa and 7 bb in a completed circuit are formed in a self-aligned manner with the P⁺ region 12 a and the N⁺ region 12 b and serve as wiring conductor layers directly connected to the P⁺ region 12 a and the N⁺ region 12 b. This simplifies the production process of a circuit.

4. In the related art, as illustrated in FIG. 13, the P⁺ region 122 and the N⁺ region 123 formed in the i layer 121 are formed so as to expand to the bottom portions of the Si pillars SP1 and SP2 and are connected to the wiring metal layer Vo through the contact hole 132 a formed on the low-resistance silicide layer 129 b formed on the upper surface of the i layer 121. Therefore, a resistance is generated in a portion of the P⁺ region 122 between the end of the silicide layer 129 b and a position directly below the Si pillar SP1 and in a portion of the N⁺ region 123 between the end of the silicide layer 129 b and a position directly below the Si pillar SP2, which reduces the driving current and the driving speed. In contrast, in this embodiment, the WSi₂ layers 7 aa and 7 bb serving as low-resistance silicide layers are directly connected to the P⁺ region 12 a and the N⁺ region 12 b on the side surfaces of the Si pillars 4 a and 4 b. This prevents formation of a resistance region formed in a portion of the P⁺ region 122 between the end of the silicide layer 129 b and a position directly below the Si pillar SP1 and in a portion of the N⁺ region 123 between the end of the silicide layer 129 b and a position directly below the Si pillar SP2 in the related art.

5. In the related art, as is clear from FIG. 13, the planar area of the contact hole 132 b that connects the output wiring metal layer Vo and the P⁺ region 122 and N⁺ region 123 decreases with increasing the density of the circuit, which increases the contact resistance. In particular, when a high-density semiconductor circuit is formed, the contact hole is formed with a minimum size in plan view to increase the density. Therefore, the increase in the contact resistance is disadvantageous. In contrast, in this embodiment, the output wiring metal layer Vout is connected to the upper surfaces and side surfaces of the WSi₂ layers 7 aa and 7 bb in the contact hole 22 d. Since the entire WSi₂ layers 7 aa and 7 bb are formed of a low-resistance silicide material, the contact resistance can be reduced by increasing the thicknesses of the WSi₂ layers 7 aa and 7 bb in the vertical direction without enlarging the shape of the contact hole 22 d in plan view.

6. In the description of this embodiment, the contact hole 22 d connected to the output wiring metal layer Vout is disposed so as to be in contact with both the WSi₂ layers 7 aa and 7 bb. However, the WSi₂ layer 7 aa containing an acceptor impurity atom and the WSi₂ layer 7 bb containing a donor impurity atom are both low-resistance silicide layers, and therefore even if the contact hole 22 d is formed on only one of the WSi₂ layers 7 aa and 7 bb, the P⁺ region 12 a and N⁺ region 12 b can be connected to the output wiring metal layer Vout at a low resistance. This can increase the degree of freedom of the position of the contact hole 22 d in the circuit design, which increases the density of the circuit.

Second Embodiment

FIG. 2AA to FIG. 2CE illustrate a method for producing a CMOS inverter circuit including an SGT according to a second embodiment of the present invention. Among FIG. 2AA to FIG. 2CD, figures suffixed with A are plan views, figures suffixed with B are sectional views taken along line X-X′ in the corresponding figures suffixed with A, figures suffixed with C are sectional views taken along line Y1-Y1′ in the corresponding figures suffixed with A, and figures suffixed with D are sectional views taken along line Y2-Y2′ in the corresponding figures suffixed with A. FIG. 2CE illustrates the relationship between Si pillars 4 a and 4 b, a P⁺ region 12 a, an N⁺ region 12 b, and CoSi₂ layers 23 aa and 23 bb in plan view.

As illustrated in FIGS. 2AA to 2AD, instead of the WSi₂ layers 7 a and 7 b in FIGS. 1EA to 1ED of the first embodiment, a CoSi₂ layer 23 a containing an acceptor impurity is formed on the periphery of the Si pillar 4 a and a CoSi₂ layer 23 b containing a donor impurity is formed on the periphery of the Si pillar 4 b.

Next, as illustrated in FIGS. 2BA to 2BD, by performing heat treatment, CoSi₂ layers 24 a and 24 b are formed on the side surfaces of the Si pillars 4 a and 4 b through silicidation. A P⁺ region 12 a is formed in the Si pillar 4 a through the forcing phenomenon of B atoms from the CoSi₂ layers 23 a and 24 a. An N⁺ region 12 b is formed in the Si pillar 4 b through the forcing phenomenon of As atoms from the CoSi₂ layers 23 b and 24 b (for the mechanism in which the CoSi₂ layers 24 a and 24 b, the P⁺ region 12 a, and the N⁺ region 12 b are formed through the forcing phenomenon of impurity atoms, refer to V. Probst, H. Schaber, A. Mitwalsky, and H. Kabza: “WSi₂ and CoSi₂ as diffusion sources for shallow-junction formation in silicon”, J. Appl. Phys. Vol. 70(2), No. 15, pp. 708-719 (1991)).

Then, by performing the same processes as those in the first embodiment, a CMOS inverter circuit illustrated in FIGS. 2CA to 2CD is formed. The P⁺ region 12 a and the N⁺ region 12 b are formed in lower portions of the Si pillars 4 a and 4 b. The CoSi₂ layers 24 a and 24 b are formed on the side surfaces of the Si pillars 4 a and 4 b so as to surround the entire peripheries of the P⁺ region 12 a and the N⁺ region 12 b. The CoSi₂ layers 23 aa and 23 bb are formed so as to surround the entire peripheries of the CoSi₂ layers 24 a and 24 b.

FIG. 2CE illustrates the relationship between the Si pillars 4 a and 4 b, the P⁺ region 12 a, the N⁺ region 12 b, the CoSi₂ layers 24 a and 24 b formed inside the Si pillars 4 a and 4 b, and the CoSi₂ layers 23 aa and 23 bb that surround the entire peripheries of the Si pillars 4 a and 4 b in plan view. The diagonally shaded area indicates the CoSi₂ layers 23 aa and 23 bb. The CoSi₂ layer 23 aa is constituted by a CoSi₂ layer 23Aa serving as a first alloy region that surrounds the entire periphery of the Si pillar 4 a in a tubular shape with an equal width and is formed in a self-aligned manner with the P⁺ region 12 a and a CoSi₂ layer 23Ab serving as a second alloy region that is partly connected to the periphery of the CoSi₂ layer 23Aa. The CoSi₂ layer 23 bb is constituted by a CoSi₂ layer 23Ba serving as a first alloy region that surrounds the entire periphery of the Si pillar 4 b in a tubular shape with an equal width and is formed in a self-aligned manner with the N⁺ region 12 b and a CoSi₂ layer 23Bb serving as a second alloy region that is partly connected to the periphery of the CoSi₂ layer 23Ba. The CoSi₂ layer 24 a serving as a third alloy layer is formed inside the Si pillar 4 a so as to be connected to the entire inner periphery of the CoSi₂ layer 23Aa serving as a first alloy region. At the same time, the CoSi₂ layer 24 b serving as a third alloy layer is formed inside the Si pillar 4 b so as to be connected to the entire inner periphery of the CoSi₂ layer 23Ba.

In this embodiment, the CoSi₂ layer 24 a serving as a third alloy layer that surrounds the entire periphery of the P⁺ region 12 a in a tubular shape with an equal width and the CoSi₂ layer 23Aa serving as a second alloy region are formed. Similarly, the CoSi₂ layer 24 b serving as a third alloy layer that surrounds the entire periphery of the N⁺ region 12 b in a tubular shape with an equal width and the CoSi₂ layer 23Ba serving as a second alloy region are formed. Thus, an electric field is uniformly applied to the P⁺ regions 12 a and the N⁺ region 12 b, and the source or drain resistance in the bottom portion of the Si pillar can be reduced compared with in the first embodiment.

Third Embodiment

FIG. 3AA to FIG. 3FD illustrate a method for producing a CMOS inverter circuit including an SGT according to a third embodiment of the present invention. Among FIG. 3AA to FIG. 3FD, figures suffixed with A are plan views, figures suffixed with B are sectional views taken along line X-X′ in the corresponding figures suffixed with A, figures suffixed with C are sectional views taken along line Y1-Y1′ in the corresponding figures suffixed with A, and figures suffixed with D are sectional views taken along line Y2-Y2′ in the corresponding figures suffixed with A.

As illustrated in FIGS. 3AA to 3AD, Si pillars 4 a and 4 b are formed on the i layer substrate 1 a by RIE using the resist layer (not illustrated), the SiO₂ layers 3 a and 3 b, and the SiN layers 2 a and 2 b as masks. Then, a SiO₂ layer 26 is entirely deposited by ALD. A SiN layer 27 is formed on the peripheries of the Si pillars 4 a and 4 b.

Next, as illustrated in FIGS. 3BA to 3BD, a resist layer 28 is formed on the SiN layer 27. Hydrogen fluoride (HF) gas is caused to flow throughout the substrate to etch the SiO₂ layer 26 that is in contact with the resist layer 28 (for the etching mechanism, refer to Tadashi Shibata, Susumu Kohyama, and Hisakazu Iizuka: “A New Field Isolation Technology for High Density MOS LSI”, Japanese Journal of Applied Physics, Vol. 18, pp. 263-267 (1979)).

Next, as illustrated in FIG. 3CA to 3CD, as a result of the etching of the SiO₂ layer 26, holes 30 a and 30 b are formed in the SiO₂ layer 26 at lower portions of the Si pillars 4 a and 4 b in a tubular shape. Thus, the SiO₂ layer 26 is divided into SiO₂ layers 26 a and 26 b that surround upper portions of the Si pillars 4 a and 4 b and a SiO₂ layer 26 c that surrounds lower portions of the Si pillars 4 a and 4 b and lies on the i layer substrate 1 a. Then, the resist layer 28 is removed. A WSi₂ layer 31 is formed on the SiN layer 27 so as to have an upper surface positioned higher than the holes 30 a and 30 b formed as a result of the etching of the SiO₂ layer 26. A SiO₂ layer 32 is formed on the WSi₂ layer 31.

Next, as illustrated in FIGS. 3DA to 3DD, a WSi₂ layer 31 a containing B atoms and a WSi₂ layer 31 b containing As atoms are formed through the same processes as those described in FIG. 1DA to FIG. 1ED of the first embodiment. By performing heat treatment, the B atoms in the WSi₂ layer 31 a are forced toward the inside of the Si pillar 4 a to form a P⁺ region 33 a and the As atoms in the WSi₂ layer 31 b are forced toward the inside of the Si pillar 4 b to form an N⁺ region 33 b.

Next, as illustrated in FIG. 3EA to 3ED, a resist layer 13 that partly covers the Si pillars 4 a and 4 b in plan view is formed through the same process as that described in FIGS. 1GA to 1GD of the first embodiment. The SiO₂ layer 32 and the WSi₂ layers 31 a and 31 b are etched by RIE using, as masks, the resist layer 13 and the SiO₂ layers 26 a and 26 b that cover the entire peripheries of the Si pillars 4 a and 4 b in plan view. Thus, WSi₂ layers 31 aa and 31 bb are formed below the SiO₂ layers 26 a and 26 b and the resist layer 13. A SiO₂ layer 32 a is left below the resist layer 13.

Next, as illustrated in FIGS. 3FA to 3FD, the resist layer 13 and the SiO₂ layers 26 a, 26 b, and 32 a are removed. A SiO₂ layer 35, a HfO₂ layer 36, and a TiN layer 37 are formed as in the case of the SiO₂ layer 14, the HfO₂ layer 15, and the TiN layer 16. Then, a CMOS inverter circuit is formed on the i layer substrate 1 a by performing the same processes as those in FIG. 1HA to FIG. 1JD of the first embodiment.

In this embodiment, the WSi₂ layers 31 aa and 31 bb, which are similar to the WSi₂ layers 7 aa and 7 bb, can be formed without forming the SiO₂ layers 11 a and 11 b on the side surfaces of the Si pillars 4 a and 4 b unlike in the first embodiment. Thus, the same advantages as those of the first embodiment are obtained.

Fourth Embodiment

FIG. 4AA to FIG. 4DD illustrate a method for producing a CMOS inverter circuit including an SGT according to a fourth embodiment of the present invention. Among FIG. 4AA to FIG. 4DD, figures suffixed with A are plan views, figures suffixed with B are sectional views taken along line X-X′ in the corresponding figures suffixed with A, figures suffixed with C are sectional views taken along line Y1-Y1′ in the corresponding figures suffixed with A, and figures suffixed with D are sectional views taken along line Y2-Y2′ in the corresponding figures suffixed with A.

In the third embodiment, as illustrated in FIGS. 3CA to 3CD, the holes 30 a and 30 b are formed, in a tubular shape, in the lower portions of the SiO₂ layers 26 a and 26 b that cover the Si pillars 4 a and 4 b. In contrast, in this embodiment, as illustrated in FIGS. 4AA to 4AD, a HfO₂ layer (not illustrated), a TiN layer (not illustrated), and a SiO₂ layer (not illustrated) that cover the Si pillars 4 a and 4 b and are formed on the SiN layer 6 are etched to form tubular holes 30A and 30B in the SiO₂ layers 26 a and 26 b at lower portions of the Si pillars 4 a and 4 b. Thus, HfO₂ layers 15A and 15B serving as gate insulating layers, TiN layers 16A and 16B serving as gate conductor layers, and SiO₂ layers 38 a and 38 b are formed so as to cover the Si pillars 4 a and 4 b. Titanium oxide (TiO) layers 39 a and 39 b are formed on surfaces of the TiN layers 16A and 16B, the surfaces facing the holes 30A and 30B.

Next, as illustrated in FIGS. 4BA to 4BD, for example, a CoSi₂ layer (not illustrated) and a SiO₂ layer 40 are formed on the SiN layer 6 so as to each have an upper surface positioned higher than the holes 30A and 30B. As in the second embodiment, a CoSi₂ layer 41 a that surrounds the Si pillar 4 a and contains B atoms and a CoSi₂ layer 41 b that surrounds the Si pillar 4 b and contains As atoms are formed by ion implantation. By performing heat treatment, the B atoms in the CoSi₂ layer 41 a are forced toward the inside of the Si pillar 4 a to form a P⁺ region 42 a, and the As atoms in the CoSi₂ layer 41 b are forced toward the inside of the Si pillar 4 b to form an N⁺ region 42 b. At the same time, CoSi₂ layers 43 a and 43 b are formed in the peripheral portions of the Si pillars 4 a and 4 b that are in contact with the CoSi₂ layers 41 a and 41 b.

Next, as illustrated in FIGS. 4CA to 4CD, a resist layer 13 that partly overlaps the top portions of the SiO₂ layers 38 a and 38 b that cover the Si pillars 4 a and 4 b is formed as in the first embodiment. The SiO₂ layer 40 and the CoSi₂ layers 41 a and 41 b are etched by RIE using the resist layer 13 and the SiO₂ layers 38 a and 38 b as masks to form a SiO₂ layer 40 a and CoSi₂ layers 41 aa and 41 bb.

Subsequently, the resist layer 13 is removed. As illustrated in FIGS. 4DA to 4DD, a SiN layer 45 is then formed on the peripheries of the Si pillars 4 a and 4 b so as to have an upper surface positioned higher than the P⁺ region 42 a and the N⁺ region 42 b. Holes that surround the TiN layers 16A and 16B are formed in the SiO₂ layers 38A and 38B so that the upper surface of the SiN layer 45 is flush with the lower ends of the holes. A NiSi layer (not illustrated) is formed on the SiN layer 45 so as to be connected to the TiN layers 16A and 16B. NiSi layers 46 a and 46 b that surround the TiN layers 16A and 16B in a tubular shape with an equal width and a NiSi layer 46 c connected to the NiSi layers 46 a and 46 are formed by the same method as the P⁺ region 42 a and the N⁺ region 42 b using the SiO₂ layers 38A and 38B as etching masks. A SiO₂ layer 47 is formed on the SiN layer 45 and the NiSi layer 46 c so as to have an upper surface positioned lower than the tops of the Si pillars 4 a and 4 b. A P⁺ region 19 a is formed in a top portion of the Si pillar 4 a and an N⁺ region 19 b is formed in a top portion of the Si pillar 4 b. A SiO₂ layer 21 is entirely formed. A contact hole 22 a is formed on the P⁺ region 19 a. A contact hole 22 b is formed on the N⁺ region 19 b. A contact hole 22C is formed on the NiSi layer 46 c. A contact hole 22 d that is connected to the upper surfaces and side surfaces of the CoSi₂ layers 41 aa and 41 bb is formed. A power supply wiring metal layer Vdd connected to the P⁺ region 19 a through the contact hole 22 a, a ground wiring metal layer Vss connected to the N⁺ region 19 b through the contact hole 22 b, an input wiring metal layer Vin connected to the NiSi layer 46 c through the contact hole 22C, and an output wiring metal layer Vout connected to the CoSi₂ layers 41 aa and 41 bb through the contact hole 22 d are formed on the SiO₂ layer 21. Thus, a CMOS inverter circuit is formed on the i layer substrate 1 a.

This embodiment provides the following advantages.

1. In this embodiment, the CoSi₂ layers 41 aa and 41 bb connected to the P⁺ region 42 a and the N⁺ region 42 b through the CoSi₂ layers 43 a and 43 b are formed on the peripheries of the Si pillars 4 a and 4 b using the SiO₂ layers 38 a and 38 b and the resist layer 13 as etching masks. As in the first embodiment, the CoSi₂ layers 41 aa and 41 bb are constituted by first alloy regions that are directly in contact with the side surfaces of the Si pillars 4 a and 4 b, that surround the entire peripheries of the Si pillars 4 a and 4 b in a tubular shape with an equal width, and that are in contact with the P⁺ region 42 a and the N⁺ region 42 b in a self-aligned manner and a second alloy region partly connected to the peripheries of the first alloy regions. In this embodiment, the peripheries of the first alloy regions are aligned with the peripheries of the SiO₂ layers 38 a and 38 b that surround the TiN layers 16A and 16B serving as gate conductor layers in plan view. This increases the density of a circuit including an SGT.

2. In this embodiment, the NiSi layers 46 a and 46 b serving as first alloy regions connected to the TiN layers 16A and 16B serving as gate conductor layers are directly in contact with the side surfaces of the TiN layers 16A and 16B, surround the entire peripheries of the TiN layers 16A and 16B in a tubular shape with an equal width, and are formed in a self-aligned manner with the TiN layers 16A and 16B. This increases the density of a circuit including an SGT.

3. In the first embodiment, the thin SiN layer 8 a and the thin HfO₂ layer 15 a lie between the WSi₂ layers 7 aa and 7 bb connected to the P⁺ region 12 a and the N⁺ region 12 b serving as drain layers and the TiN layer 16 a serving as a gate conductor layer. Therefore, there is a large capacitance between the drain P⁺ region 12 a and N⁺ region 12 b and the gate TiN layer 16 a. This inhibits the increase in the speed of the CMOS inverter circuit. In contrast, in this embodiment, a thick SiN layer 45 is formed between the NiSi layers 46 a, 46 b, and 46 c connected to the gate TiN layers 16A and 16B and the CoSi₂ layers 41 aa and 41 bb connected to the drain P⁺ region 42 a and N⁺ region 42 b. This can reduce the capacitance between the NiSi layers 46 a, 46 b, and 46 c connected to the gate TiN layers 16A and 16B and the drain P⁺ region 42 a and N⁺ region 42 b. This increases the speed of the CMOS inverter circuit.

Fifth Embodiment

FIG. 5AA to FIG. 5DD illustrate a method for producing a CMOS inverter circuit including an SGT according to a fifth embodiment of the present invention. Among FIG. 5AA to FIG. 5DD, figures suffixed with A are plan views, figures suffixed with B are sectional views taken along line X-X′ in the corresponding figures suffixed with A, figures suffixed with C are sectional views taken along line Y1-Y1′ in the corresponding figures suffixed with A, and figures suffixed with D are sectional views taken along line Y2-Y2′ in the corresponding figures suffixed with A.

As illustrated in FIGS. 5AA to 5AD, a P⁺ region 12A is formed so as to be connected to the side surface of the bottom portion of the Si pillar 4 a, and an N⁺ region 12B is also formed so as to be connected to the side surface of the bottom portion of the Si pillar 4 b. A W layer (not illustrated) is formed so as to surround the peripheries of the P⁺ region 12A and the N⁺ region 12B. A SiO₂ layer (not illustrated) is formed on the P⁺ region 12A, the N⁺ region 12B, and the W layer (not illustrated) and on the peripheries of the Si pillars 4 a and 4 b.

Subsequently, SiO₂ layers 11 a and 11 b each having an equal width in plan view are formed on the SiO₂ layer (not illustrated) so as to surround the Si pillars 4 a and 4 b by the same method as described in FIGS. 1EA to 1ED. The SiO₂ layers 11 a and 11 b are formed so that the peripheries of the bottom portions of the SiO₂ layers 11 a and 11 b protrude more outward than those of the P⁺ region 12A and the N⁺ region 12B in plan view. A resist layer 50 is formed so as to partly cover the Si pillars 4 a and 4 b and to taper in a downward direction in the drawing compared with the resist layer 13 in FIGS. 1GA to 1GD of the first embodiment in plan view. A center line A extending in a horizontal direction of the rectangular resist layer 50 in plan view does not pass through the centers of the Si pillars 4 a and 4 b. A W layer 51 and a SiO₂ layer 52 are formed by RIE using, as masks, the resist layer 50 and the SiO₂ layers 11 a and 11 b formed on the side surfaces of the peripheries of the Si pillars 4 a and 4 b as in the first embodiment. The resist layer 50 is removed.

Next, as illustrated in FIGS. 5BA to 5BD, a SiO₂ layer 14 is formed on the SiN layer 6 so as to have an upper surface that is flush with the upper surface of the SiO₂ layer 52. A HfO₂ layer 15, a TiN layer 16, and a SiO₂ layer (not illustrated) are entirely deposited. SiO₂ layers 52 a and 52 b are formed on the side surface of the TiN layer 16 that surrounds the Si pillars 4 a and 4 b by performing an etch-back process. A rectangular resist layer 53 that is connected to the Si pillars 4 a and 4 b in the upper part of the drawing so as to partly cover the Si pillars 4 a and 4 b in plan view is formed. A center line B extending in a horizontal direction of the resist layer 53 in plan view does not pass through the centers of the Si pillars 4 a and 4 b.

Next, as illustrated in FIGS. 5CA to 5CD, the TiN layer 16 is etched by RIE using, as masks, the resist layer 53 and the SiO₂ layers 52 a and 52 b formed on the side surfaces of the peripheries of the Si pillars 4 a and 4 b. Thus, a TiN layer 16 a is formed that is connected to the side surface of the HfO₂ layer 15 surrounding the Si pillars 4 a and 4 b and to a portion of the surface of the HfO₂ layer 15 on the SiO₂ layer 14. The resist layer 53 is removed. Consequently, the TiN layer 16 a is constituted by first alloy regions that are directly in contact with the side surface of the HfO₂ layer 15 surrounding the side surfaces of the Si pillars 4 a and 4 b and that are formed in a self-aligned manner so as to surround the entire periphery of the HfO₂ layer 15 in a tubular shape with an equal width and a second alloy region that is partly connected to the peripheries of the first alloy regions. The second alloy region of the TiN layer 16 a is formed so as to be, in plan view, away from the W layer 51 positioned below the resist layer 50 in FIGS. 5AA to 5AD.

Next, as illustrated in FIGS. 5DA to 5DD, a SiO₂ layer 18, a P⁺ region 19 a, an N⁺ region 19 b, and a SiO₂ layer 21 are formed as in the first embodiment. A contact hole 22 a is formed on the P⁺ region 19 a. A contact hole 22 b is formed on the N⁺ region 19 b. A contact hole 22 e is formed on the TiN layer 16 a. A contact hole 22 d is formed so as to be connected to the upper and side surfaces of the W layer 51. A power supply wiring metal layer VDD connected to the P⁺ region 19 a through the contact hole 22 a, a ground wiring metal layer VSS connected to the N⁺ region 19 b through the contact hole 22 b, an input wiring metal layer VIN connected to the TiN layer 16 a through the contact hole 22 e, and an output wiring metal layer VOUT connected to the W layer 51 through the contact hole 22 d are formed on the SiO₂ layer 21. Thus, a CMOS inverter circuit is formed on the i layer substrate 1 a.

This embodiment provides the following advantages.

1. In the first embodiment, the majority of the second alloy region of the WSi₂ layers 7 aa and 7 bb overlaps the second alloy region of the TiN layer 16 a in plan view. On the other hand, according to this embodiment, the W layer 51 corresponding to the second alloy region of the WSi₂ layers 7 aa and 7 bb does not overlap the second alloy region of the TiN layer 16 a in plan view, only a portion of the W layer 51 that surrounds the Si pillars 4 a and 4 b with an equal width overlaps the first alloy regions of the TiN layer 16 a in plan view. This can reduce the capacitance between the gate TiN layer 16 a, the drain P⁺ region 12A, and the N⁺ region 12B, which increases the speed of the CMOS inverter circuit.

2. As a result of formation of the P⁺ region 12A and the N⁺ region 12B connected to the side surfaces of the bottom portions of the Si pillars 4 a and 4 b, impurity regions serving as a source and a drain of an SGT are not necessarily formed inside the Si pillars. A W layer 51 is formed with an equal width so as to surround the P⁺ region 12A and the N⁺ region 12B in plan view. This simplifies the production of an SGT.

Sixth Embodiment

FIGS. 6AA to 6AD and FIGS. 6BA to 6BE illustrate a method for producing a CMOS inverter circuit including an SGT according to a sixth embodiment of the present invention. Among FIG. 6AA to FIG. 6BD, figures suffixed with A are plan views, figures suffixed with B are sectional views taken along line X-X′ in the corresponding figures suffixed with A, figures suffixed with C are sectional views taken along line Y1-Y1′ in the corresponding figures suffixed with A, and figures suffixed with D are sectional views taken along line Y2-Y2′ in the corresponding figures suffixed with A.

As illustrated in FIGS. 6AA to 6AD, Si pillars 4 a and 4B are formed on the i layer substrate 1 a. The Si pillar 4B is formed closer to the Si pillar 4 a than the Si pillar 4 b in the first embodiment. A SiN layer 2 a and a SiO₂ layer 3 a are formed on the Si pillar 4 a. A SiN layer 2B and a SiO₂ layer 3B are formed on the Si pillar 4B. A SiO₂ layer 6, a WSi₂ layer 7A containing B atoms, a WSi₂ layer 7B containing As atoms, and a SiN layer 8 are formed on the peripheries of the Si pillars 4 a and 4B. By performing heat treatment, a P⁺ region 12 a is formed in a portion of the Si pillar 4 a that is in contact with the WSi₂ layer 7A, and an N⁺ region 12BB is formed in a portion of the Si pillar 4 b that is in contact with the WSi₂ layer 7B. A SiO₂ film (not illustrated) is entirely deposited by CVD. The SiO₂ film is etched back by RIE to form SiO₂ layers 55 on the side surfaces of the Si pillars 4 a and 4B. The SiO₂ layers 55 are formed so as to be connected to each other in a portion between the Si pillars 4 a and 4B. A resist layer 56 that is partly in contact with the SiO₂ layers 55 in plan view is formed.

Next, as illustrated in FIGS. 6BA to 6BD, the SiN layer 8 and the WSi₂ layers 7A and 7B are etched using the SiO₂ layers 55 and the resist layer 56 as masks to form a SiN layer 8A and WSi₂ layers 7Aa and 7Bb. Subsequently, the same processes as those in the first embodiment are performed to form a CMOS inverter circuit.

FIG. 6BE illustrates the relationship between the Si pillars 4 a and 4B, the P⁺ region 12 a, the N⁺ region 12BB, and the WSi₂ layers 7Aa and 7Bb in plan view. The diagonally shaded area indicates the WSi₂ layers 7Aa and 7Bb. The WSi₂ layer 7Aa is constituted by WSi₂ layers 57 a and 57 b serving as first alloy regions that are formed in a self-aligned manner with the P⁺ region 12 a and the N⁺ region 12BB so as to surround the entire periphery of the Si pillar 4 a, WSi₂ layers 59 a and 59 b serving as second alloy regions that are partly in contact with the peripheries of the WSi₂ layers 57 a and 57 b so as to be connected to the WSi₂ layers 57 a and 57 b, WSi₂ layers 58 a and 58 b serving as third alloy regions that partly surround the peripheries of the WSi₂ layers 57 a and 57 b and are connected to the WSi₂ layers 59 a and 59 b, and a WSi₂ layer 58 c serving as a fourth alloy region that is partly connected to the WSi₂ layers 58 a and 58 b. By performing the same processes as in FIG. 1HA to FIG. 1JE, a CMOS inverter circuit can be formed on the i layer substrate 1 a.

This embodiment provides the following advantages.

1. In the first embodiment, as illustrated in FIGS. 1GA to 1GD, the SiO₂ layers 11 a and 11 b that surround the side surfaces of the Si pillars 4 a and 4 b are away from each other. In contrast, in this embodiment, the SiO₂ layers 55 are formed so as to surround the side surfaces of the Si pillars 4 a and 4 b and are connected to each other. Thus, even if the adjacent Si pillars 4 a and 4 b are brought close to each other, a CMOS inverter circuit can be formed on the i layer substrate 1 a. This increases the degree of integration of a CMOS circuit.

2. This embodiment has been described using an example in which the present invention is applied to the formation of the WSi layers 7Aa and 7Bb connected to the P⁺ region 12 a and the N⁺ region 12BB. Furthermore, the present invention is also applicable to the formation of the TiN layer 16 a serving as a gate conductor layer in the fifth embodiment. This further increases the degree of integration of a CMOS circuit.

Seventh Embodiment

FIG. 7AA to FIG. 7CD illustrate a method for producing a CMOS inverter circuit including an SGT according to a seventh embodiment of the present invention. Among FIG. 7AA to FIG. 7CD, figures suffixed with A are plan views, figures suffixed with B are sectional views taken along line X-X′ in the corresponding figures suffixed with A, figures suffixed with C are sectional views taken along line Y1-Y1′ in the corresponding figures suffixed with A, and figures suffixed with D are sectional views taken along line Y2-Y2′ in the corresponding figures suffixed with A.

As illustrated in FIGS. 7AA to 7AD, a P⁺ region 60 a and an N⁺ region 60 b are formed in a surface layer of an i layer substrate 1 by, for example, ion implantation. An i layer 1 b is formed on the P⁺ region 60 a and the N⁺ region 60 b by, for example, a Si epitaxial process. As in the first embodiment, a SiN layer 2 a, a SiO₂ layer 3 a, and a resist layer 5 a are formed on the i layer 1 b above the P⁺ region 60 a, and a SiN layer 2 b, a SiO₂ layer 3 b, and a resist layer 5 b are formed on the i layer 1 b above the N⁺ region 60 b.

Next, as illustrated in FIGS. 7BA to 7BD, the i layer 1 b, the P⁺ region 60 a, the N⁺ region 60 b, and the i layer substrate 1 are etched by RIE using the SiN layers 2 a and 2 b, the SiO₂ layers 3 a and 3 b, and the resist layers 5 a and 5 b on the i layer 1 b as masks. Thus, as in the first embodiment, a lower portion of the i layer substrate 1 is left as an i layer substrate 1 a and Si pillars 4 a and 4 b are formed on the i layer substrate 1 a. As a result of the etching of the P⁺ region 60 a and the N⁺ region 60 b, a P⁺ region 60 aa and an N⁺ region 60 bb are formed inside the Si pillars 4 a and 4 b. A SiO₂ layer 6, a WSi₂ layer 61, and a SiN layer 8 are formed on the i layer substrate 1 a on the peripheries of the Si pillars 4 a and 4 b.

Next, as illustrated in FIGS. 7CA to 7CD, the same processes as those in the first embodiment are performed. First, SiO₂ layers 11 a and 11 b are formed on the side surfaces of the peripheries of the Si pillars 4 a and 4 b. A resist layer 13 that partly covers the top portions of the Si pillars 4 a and 4 b so as to be connected to the Si pillars 4 a and 4 b is formed. The SiN layer 8 and the WSi₂ layer 61 are etched by RIE using the SiO₂ layers 11 a and 11 b and the resist layer 13 as masks to form a SiN layer 8 a and a WSi₂ layer 61 a.

Finally, the resist layer 13 is removed. Subsequently, by performing the same processes as those in the first embodiment, a CMOS inverter circuit is formed.

This embodiment provides the following advantages.

1. In this embodiment, before the formation of the WSi₂ layer 61, the P⁺ region 60 aa and the N⁺ region 60 bb are formed in the Si pillars 4 a and 4 b. Thus, as in the first embodiment, the WSi₂ layer 61 a constituted by the first alloy regions that surround the entire peripheries of the P⁺ region 60 aa and the N⁺ region 60 bb and the second alloy region that is partly in contact with the peripheries of the first alloy regions so as to be connected to the first alloy regions can be formed without forming the WSi₂ layer 7 a containing B atoms or the WSi₂ layer 7 b containing As atoms.

2. In the first embodiment, by performing heat treatment, donor or acceptor impurity atoms are forced toward the inside of the Si pillars 4 a and 4 b from the WSi₂ layer 7 a containing B atoms and WSi₂ layer 7 b containing As atoms. Thus, the P⁺ region 12 a and the N⁺ region 12 b are formed. In this case, the heat treatment conditions such as temperature and time need to be set in consideration of, for example, separation of the WSi₂ layers 7 a and 7 b caused by generation of stress. In contrast, in this embodiment, such a problem does not arise because the P⁺ region 60 a and the N⁺ region 60 b are formed before the formation of the WSi₂ layer 61. Furthermore, the impurity concentration of the P⁺ region 60 a and the N⁺ region 60 b can be sufficiently increased. This can reduce the resistance of the drain P⁺ region 60 a and N⁺ region 60 b.

Herein, as in the first embodiment, a WSi₂ layer region containing B atoms (corresponding to the WSi₂ layer 7 a in the first embodiment) and a WSi₂ layer region containing As atoms (corresponding to the WSi₂ layer 7 b in the first embodiment) may be formed. In this case, the B atoms and the As atoms are forced toward the side surfaces of the peripheries of the P⁺ region 60 aa and the N⁺ region 60 bb from the WSi₂ layer region. Thus, the P⁺ region 12 a and the N⁺ region 12 b are formed as in the first embodiment, which can further reduce the contact resistances between the P⁺ region 60 aa and the WSi₂ layer 61 a and between the N⁺ region 60 bb and the WSi₂ layer 61 a. Furthermore, even if the P⁺ region 12 a and the N⁺ region 12 b are formed to positions close to the centers of the P⁺ region 60 a and the N⁺ region 60 b and thus the P⁺ region 12 a and the N⁺ region 12 b overlap the P⁺ region 60 a and the N⁺ region 60 b, no problems arise because a high-concentration donor or acceptor impurity region is formed in the Si pillars 4 a and 4 b. The same applies to other embodiments according to the present invention.

Eighth Embodiment

FIG. 8AA to FIG. 8DD illustrate a method for producing a CMOS inverter circuit including an SGT according to an eighth embodiment of the present invention. Among FIG. 8AA to FIG. 8DD, figures suffixed with A are plan views, figures suffixed with B are sectional views taken along line X-X′ in the corresponding figures suffixed with A, figures suffixed with C are sectional views taken along line Y1-Y1′ in the corresponding figures suffixed with A, and figures suffixed with D are sectional views taken along line Y2-Y2′ in the corresponding figures suffixed with A.

As illustrated in FIGS. 8AA to 8AD, an N layer 65 is formed on a P-type substrate 1 c by, for example, epitaxial crystal growth. A P⁺ region 60 a and an N⁺ region 60 b are formed in a surface layer of the N layer 65 by performing, for example, ion implantation of phosphorus and boron. An i layer 1 b is formed on the P⁺ region 60 a and the N⁺ region 60 b by epitaxial crystal growth. As in FIGS. 1AA to 1AD, SiN layers 2 a and 2 b, SiO₂ layers 3 a and 3 b, and resist layers 5 a and 5 b are formed.

Next, as illustrated in FIGS. 8BA to 8BD, the i layer 1 b, the P⁺ region 60 a, and the N⁺ region 60 b are etched to the intermediate position of the P⁺ region 60 a and the N⁺ region 60 b in the vertical direction using the SiN layers 2 a and 2 b, the SiO₂ layers 3 a and 3 b, and the resist layers 5 a and 5 b as etching masks. Thus, Si pillars 66 a and 66 b, a P⁺ region 67 a, and an N⁺ region 67 b are formed. A SiN layer 68 is formed on the peripheries of the Si pillars 66 a and 66 b so as to have an upper surface that is flush with the upper surfaces of the P⁺ region 67 a and the N⁺ region 67 b in the Si pillars 66 a and 66 b in the vertical direction.

Next, as illustrated in FIGS. 8CA to 8CD, SiO₂ layers 69 a and 69 b are formed so as to surround the side surfaces of the Si pillars with an equal width. A SiN layer (not illustrated) is formed on the peripheries of the Si pillars 66 a and 66 b so as to have an upper surface that is flush with the upper surfaces of the SiO₂ layers 3 a and 3 b in the vertical direction. A resist layer 71 is formed so as to be partly in contact with the SiO₂ layers 69 a and 69 b in plan view. The SiN layer (not illustrated), the SiN layer 68, the P⁺ region 67 a, the N⁺ region 67 b, the N layer 65, and the P layer 1 c are etched using the SiO₂ layers 69 a, 69 b, 3 a, and 3 b and the resist layer 71 as masks. As a result of this etching, a SiN layer 70 below the resist layer, a SiN layer 68 a, a P⁺ region 67 aa, an N⁺ region 67 bb, an N layer 65 a, and a P layer 1 cc are formed.

Next, as illustrated in FIGS. 8DA to 8DD, a SiO₂ layer 75 is formed on the peripheries of the Si pillars 66 a and 66 b so as to have an upper surface positioned higher than the upper surface of the SiN layer 68 a. A HfO₂ layer (not illustrated) and a TiN layer (not illustrated) are formed on the SiO₂ layer 75 by ALD so as to cover the entire Si pillars 66 a and 66 b. SiO₂ layers 78 a and 78 b having an equal width in plan view are formed on the side surfaces of the Si pillars 66 a and 66 b so as to surround the TiN layer. A SiN layer (not illustrated) is formed on the peripheries of the Si pillars 66 a and 66 b so as to have an upper surface that is flush with the upper surfaces of the SiO₂ layers. A resist layer 81 is formed so as to partly overlap the SiO₂ layers 78 a and 78 b in plan view. The TiN layer and the HfO₂ layer are etched using the SiO₂ layers 78 a and 78 b, the SiO₂ layers 3 a and 3 b, and the resist layer 81 as masks to form TiN layers 77 a and 77 b and HfO₂ layers 76 a and 76 b. By performing the same processes as those in FIGS. 1IA to 1ID and FIGS. 1JA to 1JE, a CMOS inverter circuit including an SGT can be formed on the P layer substrate 1 cc.

This embodiment provides the following advantages.

1. In the first embodiment, the P⁺ region 12 a and the N⁺ region 12 b that lie in the bottom portions of the Si pillars 4 a and 4 b are connected to the WSi₂ layers 7 aa and 7 bb. In contrast, in this embodiment, the P⁺ region 67 aa and the N⁺ region 67 bb serving as semiconductor layers are formed in which a region corresponding to the P⁺ region 12 a, the N⁺ region 12 b, and the WSi₂ layers 7 aa and 7 bb serving as alloy layers extends from the bottom portions of the Si pillars 66 a and 66 b. That is, the P⁺ region 67 aa and the N⁺ region 67 bb serving as semiconductor layers can be used that are connected to each other on the peripheries of the Si pillars 66 a and 66 b in plan view. In this case, alloy layers that are in contact with the side surfaces of the bottom portions of the Si pillars 66 a and 66 b are not necessarily formed. This simplifies the processes. Herein, a metal layer such as a W layer or an alloy layer such as a WSi layer is desirably attached to the upper surfaces of the P⁺ region 67 aa and the N⁺ region 67 bb because the contact resistance between the P⁺ region 67 aa and the N⁺ region 67 bb can be reduced.

2. In this embodiment, as illustrated in FIGS. 8CA to 8CD, the SiN layer (not illustrated) is formed on the peripheries of the Si pillars 66 a and 66 b so as to have an upper surface that is flush with the upper surfaces of the SiO₂ layers 3 a and 3 b in the vertical direction, and the resist layer 71 that is partly in contact with the SiO₂ layers 69 a and 69 b in plan view is formed. The resist layer 71 is formed by lithography. This lithography is performed on a resist layer (not illustrated) formed on the SiO₂ layers 3 a and 3 b having upper surfaces that are flush with each other and the SiN layer (not illustrated) that surrounds the peripheries of the SiO₂ layers 3 a and 3 b. Thus, lithography can be performed on the substrate having a small difference in level compared with in the first embodiment, and therefore the resist layer 71 can be formed with high forming precision.

Ninth Embodiment

FIG. 9AA to FIG. 9BD illustrate a method for producing a CMOS inverter circuit including an SGT according to a ninth embodiment of the present invention. Among FIG. 9AA to FIG. 9BD, figures suffixed with A are plan views, figures suffixed with B are sectional views taken along line X-X′ in the corresponding figures suffixed with A, figures suffixed with C are sectional views taken along line Y1-Y1′ in the corresponding figures suffixed with A, and figures suffixed with D are sectional views taken along line Y2-Y2′ in the corresponding figures suffixed with A.

As illustrated in FIGS. 9AA to 9AD, a HfO₂ layer 83 and a TiN layer 84 are formed around the side surfaces of the Si pillars 66 a and 66 b and on the SiO₂ layer 75 by, for example, ALD. A W layer 85 is formed on the periphery of the TiN layer 84 so as to have an upper surface positioned lower than the tops of the Si pillars 66 a and 66 b. SiN layers 86 a and 86 b are formed so as to surround the side surface of the TiN layer 84 above the W layer 85 with an equal width in plan view. A resist layer 89 is formed so as to partly overlap the SiN layers 86 a and 86 b in plan view.

Next, as illustrated in FIGS. 9BA to 9BD, the W layer 85 and the TiN layer 84 are etched using the SiN layers 86 a, 86 b, 3 a, and 3 b and the resist layer 89 as masks. Thus, W layers 85 a and 85 b that surround the Si pillars 66 a and 66 b in a tubular shape with an equal width and a W layer 85 c that is partly in contact with the W layers 85 a and 85 b below the resist layer 89 are formed. In this case, the W layers 85 a, 85 b, and 85 c desirably function as etching masks for the TiN layer 84. By performing the same processes as those in FIGS. 1IA to 1ID and FIGS. 1JA to 1JE while the W layers 85 a, 85 b, and 85 c are left, a CMOS inverter circuit including an SGT can be formed on the P layer substrate 1 cc.

This embodiment provides the following advantages.

1. In the fifth embodiment, the SiO₂ layers 52 a and 52 b are formed so as to surround the entire TiN layer 16 on the side surfaces of the Si pillars 4 a and 4 b. In this case, the SiO₂ layers 52 a and 52 b need to be formed with an equal width in plan view over a long distance from the P⁺ region 12 a and the N⁺ region 12 b to the tops of the Si pillars 4 a and 4 b in the vertical direction. In contrast, in this embodiment, the SiN layers 86 a and 86 b corresponding to the SiO₂ layers 52 a and 52 b are formed with a small height so as to surround the peripheries of the top portions of the Si pillars 66 a and 66 b. Thus, the SiN layers 86 a and 86 b can be formed with high precision. The W layers 85 a and 85 b are formed on the side surfaces of the Si pillars 66 a and 66 b with a uniform thickness in the vertical direction. Therefore, the TiN layers 84 a and 84 b are formed with high precision.

2. In this embodiment, the W layers 85 a and 85 b that surround the Si pillars 66 a and 66 b in a tubular shape with an equal width and the W layer 85 c that is partly in contact with the W layers 85 a and 85 b function as gate conductor layers. Thus, a shallow contact hole (not illustrated) can be formed on the W layer 85 c in the subsequent process. Consequently, a contact hole can be formed with high precision. This increases the degree of integration of a circuit including an SGT.

Tenth Embodiment

FIGS. 10A to 10D illustrate a method for producing a CMOS inverter circuit including an SGT according to a tenth embodiment of the present invention. FIG. 10A is a plan view, FIG. 10B is a sectional view taken along line X-X′ in FIG. 10A, FIG. 10C is a sectional view taken along line Y1-Y1′ in FIG. 10A, and FIG. 10D is a sectional view taken along line Y2-Y2′ in FIG. 10A.

As illustrated in FIGS. 10A to 10D, SiN layers 91 a and 91 b are formed on a SiO₂ layer (not illustrated) that surrounds the Si pillars 66 a and 66 b so as to surround the side surfaces of the SiO₂ layers 2 a and 2 b and the SiN layers 3 a and 3 b on the tops of the Si pillars 66 a and 66 b. The SiO₂ layer (not illustrated) is etched using the SiN layers 3 a, 3 b, 91 a, and 91 b as masks to form SiO₂ layers 92 a and 92 b that surround the side surfaces of the Si pillars 66 a and 66 b with an equal width. By performing the same processes as those described in FIGS. 8CA to 8CD, the SiN layer 93 that lies below the resist layer 94 and the same P⁺ region 67 aa, N⁺ region 67 bb, N layer 65 a, and P layer 1 cc as those in FIGS. 8CA to 8CD that are connected to the bottom portions of the Si pillars 66 a and 66 b are formed.

This embodiment provides the following advantage.

In this embodiment, first, the SiN layers 91 a and 91 b that surround, with an equal width in plan view, the side surfaces of the SiO₂ layers 2 a and 2 b and the SiN layers 3 a and 3 b on the tops of the Si pillars 66 a and 66 b are formed as in the ninth embodiment. The heights of the SiN layers 91 a and 91 b can be sufficiently made smaller than those of the Si pillars 66 a and 66 b. Therefore, the SiN layers 91 a and 91 b can be formed with high precision. The SiO₂ layers 92 a and 92 b are formed on the side surfaces of the Si pillars 66 a and 66 b with a uniform thickness in the vertical direction. Thus, the SiO₂ layers 92 a and 92 b can function, with certainty, as etching masks for forming the P⁺ region 67 aa, the N⁺ region 67 bb, the N layer 65 a, and the P layer 1 cc.

Eleventh Embodiment

FIG. 11AA to FIG. 11BE illustrate a method for producing a CMOS inverter circuit including an SGT according to an eleventh embodiment of the present invention. Among FIG. 11AA to FIG. 11BD, figures suffixed with A are plan views, figures suffixed with B are sectional views taken along line X-X′ in the corresponding figures suffixed with A, figures suffixed with C are sectional views taken along line Y1-Y1′ in the corresponding figures suffixed with A, and figures suffixed with D are sectional views taken along line Y2-Y2′ in the corresponding figures suffixed with A.

As illustrated in FIGS. 11AA to 11AD, Si pillars 4 a and 4B are formed on the i layer substrate 1 a as described in FIGS. 6AA to 6AD. The Si pillar 4B is formed closer to the Si pillar 4 a than the Si pillar 4 b in the first embodiment. A SiN layer 2 a and a SiO₂ layer 3 a are formed on the Si pillar 4 a. A SiN layer 2B and a SiO₂ layer 3B are formed on the Si pillar 4B. A SiO₂ layer 6, a WSi₂ layer 7A containing B atoms, a WSi₂ layer 7B containing As atoms, and a SiN layer 8 are formed on the peripheries of the Si pillars 4 a and 4B. By performing heat treatment, a P⁺ region 12 a is formed in a portion of the Si pillar 4 a that is in contact with the WSi₂ layer 7A, and an N⁺ region 12B is formed in a portion of the Si pillar 4 b that is in contact with the WSi₂ layer 7B. A SiO₂ film (not illustrated) is entirely deposited by CVD. The SiO₂ film is etched back by RIE to form SiO₂ layers 55 on the side surfaces of the Si pillars 4 a and 4B. The SiO₂ layers 55 are formed so as to be connected to each other in a portion between the Si pillars 4 a and 4B.

Next, as illustrated in FIGS. 11BA to 11BD, the SiN layer 8 and the WSi₂ layers 7A and 7B are etched using the SiO₂ layers 55 as masks to form a SiN layer 8A and WSi₂ layers 7Aa and 7Bb. Subsequently, the same processes as those in the first embodiment are performed to form a CMOS inverter circuit.

FIG. 11BE illustrates the relationship between the Si pillars 4 a and 4B, the P⁺ region 12 a, the N⁺ region 12B, and the WSi₂ layers 7Aa and 7Bb in plan view. The diagonally shaded area indicates the WSi₂ layers 7Aa and 7Bb. The WSi₂ layer 7Aa is constituted by WSi₂ layers 57 a and 57 b serving as first alloy regions that are formed in a self-aligned manner with the P⁺ region 12 a and the N⁺ region 12B so as to surround the entire periphery of the Si pillar 4 a, WSi₂ layers 59 a and 59 b serving as second alloy regions that are partly in contact with the peripheries of the WSi₂ layers 57 a and 57 b so as to be connected to the WSi₂ layers 57 a and 57 b, and WSi₂ layers 58 a and 58 b serving as third alloy regions that partly surround the peripheries of the WSi₂ layers 57 a and 57 b and are connected to the WSi₂ layers 59 a and 59 b. By performing the processes in FIG. 1HA to FIG. 1JE, a CMOS inverter circuit can be formed on the i layer substrate 1 a.

This embodiment provides the following advantages.

1. In this embodiment, the WSi₂ layers 7Aa and 7Bb are formed without using the resist layer 56 described in the sixth embodiment. In this case, the SiO₂ layers 55 that surround the Si pillars 4 a and 4B are formed so as to have a larger width in plan view, a contact hole (not illustrated) is formed on the WSi₂ layers 7Aa and 7Bb, and the connection to the upper metal wiring (not illustrated) can be achieved. This simplifies the processes. Furthermore, the Si pillars 4 a and 4B are formed close to each other, which increases the density of a circuit.

2. This embodiment is also applicable to formation of a gate conductor layer as in the sixth embodiment. This further increases the density of an SGT circuit.

In each of the above embodiments, a Si pillar made of silicon has been used. However, the technical idea of the present invention is applicable to SGTs partly or wholly formed of a semiconductor material other than silicon.

In each of the above embodiments, the case where the Si pillars 4 a, 4 b, and 4B have a circular shape in plan view has been described. However, it is obvious that the Si pillars 4 a, 4 b, and 4B may have an elliptical or rectangular shape.

In the first embodiment, the material layers that surround the peripheries of the Si pillars 4 a and 4 b and are to be etched with an equal width are the WSi₂ layers 7 a and 7 b connected to the P⁺ region 12 a and the N⁺ region 12 b. In the second embodiment, the material layers to be etched are the CoSi₂ layers 23 a and 23 b connected to the P⁺ region 12 a and the N⁺ region 12 b. In the fifth embodiment, the material layer to be etched is the TiN layer 16. In the eighth embodiment, the material layers to be etched are the P⁺ region 67 a and the N⁺ region 67 b that are semiconductor layers containing a donor or acceptor impurity. In the ninth embodiment, the material layer to be etched is the W layer 85 serving as a metal layer. As described above, the material layers to be etched in the present invention are conductive layers such as alloy layers, metal layers, and semiconductor layers containing a donor or acceptor impurity.

In the first embodiment, the SiO₂ layers 11 a and 11 b that surround the side surfaces of the Si pillars 4 a and 4 b have been used as etching masks for the WSi₂ layers 7 a and 7 b connected to the P⁺ region 12 a and the N⁺ region 12 b. Instead of the SiO₂ layers 11 a and 11 b, a material layer formed of one or more layers may be used. When the WSi₂ layers 7 a and 7 b are changed to other conductive layers, another material layer that functions as an etching mask may be used. The same applies to the SiO₂ layers 2 a and 2 b and the SiN layers 3 a and 3 b that lie on the tops of the Si pillars 4 a and 4 b and prevent the Si pillars 4 a and 4 b from being etched. Instead of the SiO₂ layers 2 a and 2 b and the SiN layers 3 a and 3 b, other material layers that function as etching masks and are formed of one or more layers may be used. In the fifth embodiment, the SiO₂ layers 52 a and 52 b that surround the side surface of the TiN layer 16 to serve as a gate conductor layer have been used as etching masks. The same also applies to the case where the present invention is applied to the gate conductor layer. The same also applies to other embodiments according to the present invention.

In the first embodiment, the resist layer 13 has been used as an etching mask. However, an organic or inorganic material layer formed of one or more layers may be formed below a resist layer for lithography, and such a material layer may be used as a mask material layer. The same applies to other embodiments according to the present invention.

In the first embodiment, the TiN layer 16 a has been used as a gate conductive layer. However, the gate conductive layer may be a different metal layer or a conductor material layer. The gate conductor layer may be a multilayer conductor layer. The same applies to other embodiments according to the present invention.

In the first embodiment, the SiO₂ layer 6, the WSi₂ layer 7, and the SiN layer 8 have been formed by sputter deposition, but they may be formed by entirely depositing material layers by, for example, CVD and then etching back the material layers. Alternatively, another method may be employed in which any of the SiO₂ layer 6, the WSi₂ layer 7, and the SiN layer 8 is formed by an etch-back process and the other is formed by a sputtering process. The same applies to other embodiments according to the present invention.

In the first embodiment, the case where the side surfaces of the Si pillars 4 a and 4 b have a columnar shape that is vertical to the plane of the i layer substrate has been described. However, the side surfaces of the Si pillars 4 a and 4 b may have a trapezoidal shape or a barrel-like shape as long as the structure in each embodiment is realized. The same applies to other embodiments according to the present invention.

In the first embodiment, the description has been made using the WSi₂ layers 7 a and 7 b. However, for example, a silicide layer containing another metal atom, an alloy layer containing a semiconductor atom other than Si, or a semiconductor layer containing an impurity atom may be used as long as the structure in this embodiment is realized. The same applies to other embodiments according to the present invention.

In the first embodiment, the P⁺ regions 12 a and 33 a and the N⁺ regions 12 b and 33 b are formed on the peripheries of the Si pillars 4 a and 4 b. In the fourth embodiment, the P⁺ region 42 a and the N⁺ region 42 b are formed so as to extend to the centers of the Si pillars 4 a and 4 b. In both the embodiments, the depth of such a P⁺ region and an N⁺ region formed in the Si pillars 4 a and 4 b varies depending on the width of the Si pillars 4 a and 4 b and the temperature in the processes. As a result, such a P⁺ region and an N⁺ region may be formed to the peripheries of the Si pillars 4 a and 4 b or to the centers of the Si pillars 4 a and 4 b. The same applies to other embodiments according to the present invention.

In the first embodiment, the description has been made using the WSi₂ layers 7 aa and 7 bb as wiring alloy layers. In this case, almost no silicide layer is formed in the Si pillars 4 a and 4 b. However, when the interface between the WSi₂ layers 7 aa and 7 bb and the Si pillars 4 a and 4 b is observed under magnification, a thin silicide layer is formed in the Si pillars depending on the heat treatment conditions in the processes. Therefore, the WSi₂ layers 7 aa and 7 bb may be connected to the P⁺ regions 12 a and 12 b on the peripheries of the Si pillars 4 a and 4 b or inside the Si pillars 4 a and 4 b in plan view. The same applies to other embodiments according to the present invention.

In the first embodiment, as illustrated in FIGS. 1GA to 1GD, the resist layer 13 that partly overlaps the Si pillars 4 a and 4 b in plan view is formed. The SiN layer 8 and the WSi₂ layers 7 a and 7 b are etched by RIE using the resist layer 13, the SiO₂ layers 11 a and 11 b, the SiO₂ layers 2 a and 2 b, and the SiN layers 3 a and 3 b as masks to form a SiN layer 8 a and WSi₂ layers 7 aa and 7 bb. As a result of this etching, a part or the entirety of the SiN layers 3 a and 3 b may be removed as long as the top portions of the Si pillars 4 a and 4 b are not etched at the end of the etching. The SiO₂ layers 11 a and 11 b, the SiO₂ layers 2 a and 2 b, and the SiN layers 3 a and 3 b may be changed to other material layers formed of one or more layers as long as they function as etching masks. The same applies to other embodiments according to the present invention.

In the first embodiment, a well layer is not formed in lower portions of the Si pillars 4 a and 4 b below the P⁺ region 12 a and the N⁺ region 12 b. However, after the formation of the Si pillars 4 a and 4 b, a well layer formed of one or more layers may be formed by, for example, ion implantation or solid-state diffusion. This does not depart from the scope of the present invention at all. The same applies to other embodiments according to the present invention.

In the first embodiment, the HfO₂ layer 15 a has been used as an insulating layer. However, the material for the insulating layer is not limited to HfO₂, and another insulating layer formed of one or more layers may be used. The same applies to other embodiments according to the present invention.

In the first embodiment, the case where a single SGT is formed in each of the Si pillars 4 a and 4 b has been described. However, since the present invention relates to the P⁺ region 12 a and the N⁺ region 12 b formed in the bottom portions of the Si pillars 4 a and 4 b and to the WSi₂ layers 7 aa and 7 bb serving as wiring alloy layers connected to the P⁺ region 12 a and the N⁺ region 12 b, the present invention is applicable to formation of a circuit including a plurality of SGTs in a single semiconductor pillar. The same applies to other embodiments according to the present invention.

In the descriptions of the second embodiment and the fourth embodiment, the CoSi₂ layers 24 a, 24 b, 43 a, and 43 b serving as silicide layers are formed on the peripheries of the Si pillars 4 a and 4 b. The formation of the silicide layers to the centers of the Si pillars 4 a and 4 b does not depart from the scope of the present invention at all. The same applies to other embodiments according to the present invention.

In the fourth embodiment, the TiN layers 16A and 16B and the NiSi layer 46 serving as a wiring conductor layer are connected to each other at the intermediate positions of the TiN layers 16A and 16B in the vertical direction. This reduces the capacitance between the gate TiN layers 16A and 16B and the source P⁺ region 42 a and N⁺ region 42 b. The same applies to other embodiments according to the present invention.

In the fifth embodiment, as illustrated in FIGS. 5AA to 5AD, the P⁺ region 12A is formed so as to be connected to the side surface of the bottom portion of the Si pillar 4 a, and the N⁺ region 12B is formed so as to be connected to the side surface of the bottom portion of the Si pillar 4 b. Then, the TiN layer 16 a serving as a gate conductor layer is formed. However, as described in the fourth embodiment, the P⁺ region 12A and the N⁺ region 12B may be formed by forming the TiN layers 16A and 16B serving as gate conductor layers and then forming the holes 30A and 30B in the layers overlying the Si pillars 4 a and 4 b at bottom portions of the Si pillars 4 a and 4 b so that the P⁺ region 12A is connected to the side surface of the bottom portion of the Si pillar 4 a and the N⁺ region 12B is connected to the side surface of the bottom portion of the Si pillar 4 b. In this case, as illustrated in FIGS. 5AA to 5AD, the P⁺ region 12A containing an acceptor impurity may be formed by, for example, selective epitaxial crystal growth after the formation of the hole 30A, and then the N⁺ region 12B containing a donor impurity may be formed by, for example, selective epitaxial crystal growth after the formation of the hole 30B. Subsequently, a W layer (not illustrated) is formed by, for example, selective epitaxial crystal growth so as to be connected to the side surfaces of the P⁺ region 12A and the N⁺ region 12B. The periphery of the W layer in plan view is desirably aligned with the peripheries of the SiO₂ layers 38 a and 38 b in FIGS. 4AA to 4AD. Subsequently, another W layer (not illustrated) is formed by, for example, sputter deposition so as to be in contact with the periphery of the W layer formed by selective epitaxial crystal growth. Then, by performing the same processes as those illustrated in FIG. 4BA to FIG. 4DD, a CMOS inverter circuit is formed. The P⁺ region 12A and the N⁺ region 12B may be formed by a method other than selective epitaxial crystal growth. The same applies to the formation of the W layer 51. The P⁺ region 12A and the N⁺ region 12B may be semiconductor material layers made of a material other than Si, such as SiGe layers containing a donor or acceptor impurity. Regarding the W layer 51, a buffer conductor layer formed of one or more layers for reducing the contact resistance between the W layer and the P⁺ region 12A and N⁺ region 12B may be disposed between the W layer and the P⁺ region 12A and N⁺ region 12B. The same applies to other embodiments according to the present invention.

The P⁺ region 12A and the N⁺ region 12B in the fifth embodiment may be made of a semiconductor material, such as SiGe, that is different from the semiconductor material for the Si pillars 4 a and 4 b. The same applies to other embodiments according to the present invention.

In the fifth embodiment, the W layer 51 and the TiN layer 16 a are formed so that the W layer 51 and a portion of the TiN layer 16 a that extends in a horizontal direction do not overlap each other in plan view. This reduces the capacitance between the W layer 51 and the TiN layer 16 a. The same effect is also produced by decreasing the size of the overlapping portion. The same applies to other embodiments according to the present invention.

In the fifth embodiment, the rectangular resist layers are formed so that the center lines A and B of the resist layers extend so as not to pass through the center points of the Si pillars 4 a and 4 b. However, only one of the center lines may extend so as not to pass through the center points of the Si pillars 4 a and 4 b. In this embodiment, two Si pillars 4 a and 4 b are employed, but one Si pillar may be employed. The same applies to other embodiments according to the present invention.

In the fifth embodiment, the P⁺ region 12A and the N⁺ region 12B are formed so as to be in contact with the side surfaces of the bottom portions of the Si pillars 4 a and 4 b. A P⁺ region and an N⁺ region may be formed inside the Si pillars 4 a and 4 b through thermal diffusion of impurities caused by heat treatment after the formation of the P⁺ region 12A and the N⁺ region 12B. The same applies to other embodiments to which this embodiment can be applied.

In the sixth embodiment and the eleventh embodiment, the description has been made using an example in which the present invention is applied to a CMOS inverter circuit. The present invention can also be applied to formation of a circuit in which SGTs formed in the Si pillars 4 a and 4 b while the P⁺ region 12 a is changed to an N⁺ region containing a donor impurity are connected in parallel. This circuit is used when a large electric current is required. A high-density circuit is easily formed because the N⁺ regions are connected in parallel and the gate conductor layers are connected in parallel. The electric current is increased by increasing the number of SGTs formed in parallel.

In the ninth embodiment, the W layers 85 a and 85 b serving as conductor layers have been formed so as to be in contact with the side surfaces of the TiN layers 84 a and 84 b. The W layers 85 a and 85 b may be other material layers such as conductor layers or insulating layers as long as they function as etching masks for the TiN layer 84. The W layers 85 a and 85 b may also be multilayer material layers.

In the first embodiment, the SiN layers 2 a and 2 b and the SiO₂ layers 3 a and 3 b on the Si pillars 4 a and 4 b are used as etching masks for the WSi₂ layers 7 a and 7 b. By changing the WSi₂ layers 7 a and 7 b to other conductive material layers or selecting another etching gas, the WSi₂ layers 7 aa and 7 bb or other conductive material layers may be formed while the SiN layers 2 a and 2 b and the SiO₂ layers 3 a and 3 b are not present. For the SiN layers 2 a and 2 b and the SiO₂ layers 3 a and 3 b, for example, in the process in FIGS. 8BA to 8BD, a SiO₂ layer is formed so as to cover the Si pillars 66 a and 66 b and polished by CMP so as to have an upper surface that is flush with the upper surfaces of the SiN layers 2 a and 2 b. The SiN layers 2 a and 2 b are removed and then mask material layers such as SiN layers and SiO₂ layers may be additionally formed on the tops of the Si pillars 66 a and 66 b. It is sufficient that mask material layers such as SiN layers and SiO₂ layers are formed before the resist layer 71 is formed. The same applies to other embodiments to which this embodiment can be applied.

In the first embodiment, as illustrated in FIGS. 1JA to 1JE, the WSi₂ layers 7Aa (7 aa) and 7Ba (7 bb) are formed that are constituted by the first alloy regions that are directly in contact with the side surfaces of the Si pillars 4 a and 4 b, surround the entire peripheries of the Si pillars 4 a and 4 b in a tubular shape with an equal width in plan view, and are in contact with the P⁺ region 12 a and the N⁺ region 12 b in a self-aligned manner and the second alloy region that is connected to the first alloy regions and extends in a horizontal direction. In the fifth embodiment, as illustrated in FIGS. 5CA to 5CD, the TiN layer 16 a is formed that is constituted by the first alloy regions that are in contact with the gate TiN layers 16 a and 16 b in a self-aligned manner so as to surround the entire peripheries in a tubular shape with an equal width in plan view and the second alloy region that is connected to the first alloy regions and extends in a horizontal direction. As described above, the first alloy regions and the second alloy region that are connected to the P⁺ region 12 a and the N⁺ region 12 b and the first alloy regions and the second alloy region that are connected to the gate TiN layers 16 a and 16 b are formed by fundamentally the same method. Thus, the present invention can be applied to at least one of the formation of the first alloy regions and the second alloy region that are connected to the P⁺ region 12 a and the N⁺ region 12 b and the formation of the first alloy regions and the second alloy region that are connected to the gate TiN layers 16 a and 16 b. The same applies to other embodiments to which this embodiment can be applied.

In the first embodiment, as illustrated in FIGS. 1FA to 1FD, the P⁺ region 12 a and the N⁺ region 12 b are formed by causing an acceptor or donor impurity to thermally diffuse from the WSi₂ layers 7 a and 7 b containing an acceptor or donor impurity. For the P⁺ region 12 a and the N⁺ region 12 b, the WSi₂ layers 7 a and 7 b do not necessarily contain an acceptor or donor impurity in the case where the P⁺ region 60 a and the N⁺ region 60 b in the seventh embodiment are formed in the previous process. In this case, the WSi₂ layers 7 a and 7 b may be conductor layers formed of other material layers. The first alloy regions and the second alloy region may be first conductive regions and a second conductive region formed of another conductive material. The same applies to other embodiments to which this embodiment can be applied.

In the first embodiment, the WSi₂ layers 7 aa and 7 bb are used as wiring alloy layers. However, conductive layers that have an equal width in plan view and are formed of one or more layers may be used. The same applies to other embodiments to which this embodiment can be applied.

In the fifth embodiment, as illustrated in FIGS. 5AA to 5AD, the P⁺ region 12A is formed so as to be connected to the side surface of the bottom portion of the Si pillar 4 a, and similarly the N⁺ region 12B is formed so as to be connected to the side surface of the bottom portion of the Si pillar 4 b. The W layer 51 is formed so as to surround the peripheries of the P⁺ region 12A and the N⁺ region 12B. As described above, the region corresponding to the first alloy region in the first embodiment is constituted by two regions, that is, the P⁺ region 12A and the W layer 51. Similarly, the region corresponding to the first alloy region is constituted by two regions, that is, the N⁺ region 12B and the W layer 51. The first alloy (conductive) region may be constituted by a plurality of conductive layers having an equal width in plan view. The same applies to other embodiments to which this embodiment can be applied.

In the fifth embodiment, as illustrated in FIGS. 5CA to 5CD, the gate TiN layer 16 a is constituted by the first alloy regions (first conductive regions) that surround the Si pillars 4 a and 4 b with an equal width and the second alloy region (second conductive region) connected to the first alloy regions of the Si pillars 4 a and 4 b. As described above, the first alloy regions and the second alloy region are formed of the same material layer. The same applies to other embodiments to which this embodiment can be applied.

In the fourth embodiment, the NiSi layers 46 a and 46 b serving as first alloy regions are formed with an equal width in plan view so as to be connected to the gate TiN layers 16A and 16B, and the NiSi layer 46 c serving as a second alloy region is formed so as to be connected to the NiSi layers 46 a and 46 b serving as first alloy regions. As described above, the first alloy regions and the second alloy region can be formed through connection at the intermediate positions of the gate TiN layers 16A and 16B in the vertical direction. The same applies to other embodiments to which this embodiment can be applied.

The SiO₂ layers 92 a and 92 b and the SiN layer 93 in the tenth embodiment may be other material layers or may be multilayer material layers.

In each of the above embodiments, a SOI (silicon on insulator) substrate including an insulating substrate may also be used instead of the i layer substrate 1 a.

The SGT has a structure in which a gate insulating layer is formed on a periphery of a semiconductor pillar and a gate conductor layer is formed on a periphery of the gate insulating layer. A flash memory device including a conductor layer electrically floating between the gate conductor layer and the gate insulating layer is also one embodiment of the SGT, and the technical idea of the present invention can be applied to such a flash memory device.

In the present invention, there are provided at least a first conductive region that surrounds the entire periphery of a source or drain impurity region in the lower portions of the Si pillars 4 a, 4 b, and 4B and a second conductive region that is partly connected the periphery of the first conductive region in plan view. For example, in a circuit including a plurality of SGTs connected in parallel on the same substrate to increase the driving current, the circuit being different from the circuit having the features of the present invention, the second conductive region may be connected to a plurality of portions of the periphery of the first conductive region or to the entire periphery of the first conductive region.

In each of the above embodiments, the case where only an SGT is formed in the semiconductor pillar has been described. However, the technical idea of the present invention is applicable to a method for producing a semiconductor device including an SGT and an element (e.g., a photodiode) other than the SGT incorporated therein.

In each of the above embodiments, the description has been made using an SGT in which the upper and lower impurity regions serving as sources or drains contain impurity atoms having the same polarity. However, the present invention is also applicable to a tunneling SGT including impurity atoms having different polarities. Similarly, the present invention is also applicable to an SGT in which at least one of the source and the drain is formed using a Schottky diode.

In each of the above embodiments, the description has been made using the i layer substrates 1 and 1 a and the P layer substrates 1 c and 1 cc. However, for example, a well structure or a SOI substrate may be employed in accordance with the required performance.

Various embodiments and modifications of the present invention can be made without departing from the broad spirit and scope of the present invention. The above-described embodiments are illustrative examples of the present invention and do not limit the scope of the present invention. The above-described embodiments and modifications can be freely combined with each other. Furthermore, embodiments from which some of constituent features of the embodiments are removed as required are also within the technical idea of the present invention.

The semiconductor device including an SGT according to the present invention and the method for producing the semiconductor device are useful for realizing a high-density semiconductor device including an SGT. 

What is claimed is:
 1. A semiconductor device including a surround gate MOS transistor (SGT), comprising: a first semiconductor pillar that stands on a substrate in a direction vertical to a plane of the substrate; a first gate insulating layer that surrounds the first semiconductor pillar; a first gate conductor layer that surrounds the first gate insulating layer; a first impurity region that is positioned below the gate conductor layer in the vertical direction and is connected to a portion inside the first semiconductor pillar or to a side surface of the first semiconductor pillar; a first conductive layer that surrounds an entire periphery of the first impurity region in a plan view; a second conductive layer that is partly connected to a periphery of the first conductive layer in the plan view and extends in a direction horizontal to the plane of the substrate; a third conductive layer that surrounds an entire periphery of the first gate conductor layer in the plan view; and a fourth conductive layer that is partly connected to a periphery of the third conductive layer in the plan view, extends in a direction horizontal to the plane of the substrate, and partly overlaps the second conductive layer or does not overlap the second conductive layer in the plan view, wherein at least one of the first conductive layer and the third conductive layer has an equal width in the plan view. 